A systematic, random sample of 450 small and mixed-animal practitioners was selected from the client list of a prominent veterinary pharmaceutical and animal health company. A telephone survey was conducted, using a standard questionnaire, to assess whether current veterinary practices concerning prophylaxis and treatment of canine roundworm (Toxocara canis) and hookworm (Ancylostoma spp) infections are adequate to prevent transmission to human beings. Analysis of results focused on 3 questions related to prevention: practitioner's frequency of client education regarding zoonotic potential of roundworms and hookworms, pup age at which veterinarian recommends first anthelmintic treatments, and proportion of veterinarians recommending prophylactic drug administration for pups and nursing bitches. Despite the proven association of household pet dogs and human toxocariasis, only a third (148/450) of veterinarian respondents routinely discussed the potential zoonotic hazards of canine roundworms with their clients. A total of 29% (130/450) of veterinarians surveyed either never discussed these potential hazards or discussed them only when asked by their clients. With regard to anthelmintic treatment practices, 31% (140/450) of veterinarians surveyed recommended that pups first be examined and treated for intestinal parasites within 4 weeks of age. Thirty-three percent (163/450) recommended first examination and deworming at 5 to 6 weeks of age, and 36% (163/450) suggested that it be done at or after 7 weeks of age. Less than half (208/450) of veterinarians administered anthelmintics prophylactically to at least some pups and dogs. Sixty-four percent (287/450) of respondents recommended routine testing and treatment of nursing bitches.(ABSTRACT TRUNCATED AT 250 WORDS)