A wide range of parasites can infect carnivorous pets. Some are more significant than others, owing to their prevalence, their pathogenicity for animal hosts, or their capacity to cause human disease. This article focuses on roundworms (Toxocara spp.) and tapeworms (Echinococcus spp.), which are emerging public health hazards in France. When humans ingest infective Toxocara eggs, the eggs hatch and release larvae that can migrate anywhere in the body, causing a disease called visceral larva migrans. Common target organs are the eyes, brain, liver, and lungs, with a risk of permanent visual, neurological and other tissue damage. Epidemiological studies have identified geophagy and pet dogs (particularly puppies) as the principal risk factors for human toxocarosis. Childrens' play habits and their attraction to pets put them at a higher risk for infection than adults. Eggs of the dog tapeworm Echinococcus granulosus hatch and release embryos that migrate to various organs and form voluminous cysts, causing a disease called cystic echinococcosis. Human alveolar echinococcosis is caused by the larval stage of the fox tapeworm Echinococcus multilocularis, which usually develops in the liver. Larval growth is slow, resulting in an asymptomatic phase of several years before diagnosis. Left untreated, the condition may be lethal. In central and eastern European areas where Echinococcus multilocularis is endemic, dogs that have access to rodents should be considered as potential hazards for humans. Rational measures for preventing animal and human infection include pet owner education and regular deworming of dogs and cats. Education of pet owners should focus on prevention, and will include personal hygiene, clearing up pet feces regularly to reduce environmental contamination, and minimizing exposure of children to potentially contaminated environments. Because puppies, kittens, pregnant and nursing animals and hunting dogs are at the highest risk of roundworm or tapeworm infection--and are therefore responsible for most environmental contamination and human disease--antihelminthic treatments are most effective when they are initiated early and target these animal populations. Various guidelines for the treatment and control of parasitic infections in carnivorous pets have been proposed in the United States (by the Centers for Disease Control and Prevention, and the Companion Animal Parasitology Council) and in Europe (by the European Scientific Counsel Companion Animal Parasitology). In France a non profit organization (CEPHA, Comité d'Experts en Parasitologie Humaine et Animale) was recently created to participate in the prevention of parasitic zoonoses associated with companion animals.