I am simply amazed by this product - The Feliway pheromone diffuser
http://www.feliway.com/us
It was recommended by our vet and appears to be 100% effective for our latest problem cat. Our older male cat had started spraying in the house. Over the last twenty years, we have tried any number of products that are supposed to stop this behavior - TOO MANY - but none worked for any cat. We plugged this thing in and the spraying stopped immediately! After a month or so, when the diffuser ran dry, it couldn't have more than a day or two before Isaac sprayed again. We WILL be getting a refill unit today [they were sold out yesterday].
Also, the cats seem to love it. Isaac started sleeping on the floor next to the diffuser.