I love this stuff, its great and works fine...however it is very important to apply the product monthly as well as correctly. I have thought for years with the Cats I have had, as well as have been told by several vets and vet techs over the years; that the correct way to apply this product is directly on the skin between the shoulder blades. And to be fair to most of the Vets whom have told me that, for the most part I was successful using that method of application. However, as time went on I found this way to apply Frontline more and more difficult as well as it always seem uncomfortable for the Cat. You can use the space between your Cat's shoulder blades as a guide - BUT - the exact proper application spot is actually higher up - at the base of the skull (or as worded inside the package if your Frontline came with the proper instructions `at the base of the neck'). I was very pleasantly surprised that this method was not only much easier, but that there was also no wasted product...I was able to quickly and easily apply the product to each of our 3 cats. I also noticed right away two things. One, each Cat was pretty much comfortable right away and fine as they were before I applied the product - as if I had not even treated them at all. Two, the product was at a spot the cats could not reach even if they wanted to. I don't know why I had never heard of this application method before, as well as why all of the Frontline (and related products) I had purchased in the past said to apply the product directly onto the skin "Between the shoulder blades". This product is great and does work, but it is very important that you apply the product once every 30 days. I would suggest picking a particular date of the month and sticking with that date each and every month. (If you are ever off by a day or two, that is fine - just remember to try and not let it go over 30 days if possible.) Frontline Plus for Cats is not intended to last longer than 30 days, and while it may for some Cats - I personally would not recommend going past the 30 days. If your Cats have worms, this product will keep off the new fleas yes but will do nothing for worms - you should de-worm your Cats first (if needed) and then start with the Frontline about 3 days after de-worming. Indoor Cats can get worms from fleas, even in a very clean home - from time to time some fleas will get in (whether it's on your shoes or from leaving your doors open, etc). Cats usually get worms from when fleas get on them, and then as the cat as it's grooming itself - the cat ingests the fleas (of course the Cat has no idea this will give them worms - they are just cleaning themselves as Cats do). When a Cat eats fleas or other parasites that can get on them from time to time, they can also get other things if left untreated such as Heartworms which are usually fatal. However there is good news! Just apply Frontline once every 30 days and your Cat will stay Flea and parasite free! Any fleas or anything else that may from time to time get onto your Cat will die right away and be of no risk to your Cat. Also over time any residual fleas will eventually die off and your home will be flea - free! However you must apply this product every 30 days year round to ensure that Fleas do not return to your Cat! Preventing your cat from having fleas will in turn not only make you cat much more comfortable, but will also prevent more serious things such as Tapeworms, Roundworms and Heartworms to name just a few things that can originate from your cat ingesting fleas. These more serious conditions for Cats can be prevented with a monthly flea treatment such as Frontline Plus for example. If your cat or home is for some reason very infested with fleas - you have to address that problem first! Remove the cats from the home and use "Flea Bombs" if needed, at least that's how I have always heard them referred to while the proper term is yes "Flea Fogger" or even "Fumigator". You can also use sprays or other like products for your carpet and furniture. Once the home is flea free and your Cat has been treated at the vet for fleas, then make sure to stick with the Frontline every 30 days thereafter. You can also use the Frontline liquid spray to initially kill fleas on the Cat, or a Flea Shampoo. Also keep in mind if your Cat and home are heavily infested with fleas, you should de-worm your cat as well. For most people, de-worming should only be done by or under the direction of a reputable Veterinarian. However if you have owned Cats for many years and know what meds to buy, you can de-worm cats on your own -BUT- only if you are a VERY experienced Cat owner. You can kill your Cat if you give it the wrong type or too much of a de-wormer as de-wormer is a poison (though it's this poison that kills the worms and is perfectly safe when used properly). Frontline helps to keep your cat healthy and is a great preventative medication for your cat. Frontline can and will help keep your Cat healthy and happy for many years to come! Also keep in mind Frontline does not replace periodic checkups or help your Cat in any way if he or she is injured though it will go a very long way in preventing many Cat illnesses and problems related to fleas, ticks, and common parasites. There is more you can do to keep fleas away too, such as treating your yard (unless you have an apartment or condo, etc.) with Pesticide Granules such as Ortho or whatever brand works for you. I am in the Midwest and I would say twice a year is good for the yard treatment, but in South Carolina where I used to live I would have to treat the yard 3 - 4 times a year. If your Cat is outdoor only, keep the Cat inside for 3 -5 days (personally I would say no less than 5 days if possible - a week is more than enough if you want to be extra sure), the same applies for indoor-outdoor cats. This will give the Pesticide time to get into the ground so that it's not toxic to your Cat or small animals such as birds that your Cats may go after. I also use the Riddex Pest repellers....every little bit helps! And of course most importantly of all, apply the Frontline once every 30 days.