A review is presented of the biology, epizootiology, pathogenesis, clinical features, diagnosis and treatment of canine and feline Ctenocephalides canis and C. felis infestation. Also data are given on the prevalence of fleas in dogs and cats during a year at the 1st Animal Medical Hospital, Munich Veterinary Faculty. 5.5% of the dogs and 18.9% of the cats were infested with fleas.