Stray dogs and cats are a common sight on the Greek Islands. Overpopulation increases spread of infectious diseases and transmission of zoonotic agents. Population control must be performed on different levels including legislation, registration/identification, garbage control, habitat control, neutering of pets and stray dogs and cats, control of breeders/sales, and education of the public. Evaluative studies are essential for the selection of a protocol and may lead to a different approach for each species. The purpose of the study reported here was to evaluate the roots of the stray cat and dog problem and to monitor the success of a catch-neuter-release program on one Greek island. This report should offer a practical guideline to Non Government Organizations (NGO's) and municipalities for a successful population control program.