The anthelmintic effects of levamisole (100-50 mg kg-1 live bodyweight), ivermectin (2 mg kg-1 bodyweight), albendazole and fenbendazole (both 100 mg kg-1 bodyweight), were tested against second stage Toxocara canis larvae in mice. Anthelmintic treatment on days 2 to 7 after infection inclusive resulted in significant (P less than 0.05) retention of larvae in the liver, and fewer larvae migrated subsequently to the brain and the musculature of treated mice compared to untreated controls. Most of the larvae retained in the liver subsequently died there and were not recoverable by day 35 after infection, causing significant (P less than 0.05) reduction in the total larval recoveries compared to the controls. The oral route of drug administration caused higher larval retention in the liver than the subcutaneous route. All infected levamisole treated mice survived for four months, whereas half the similarly infected but untreated mice died within the same period. Treatment on days 8 to 13 inclusive after infection had no effect on second stage T canis larvae suggesting that once the larvae have reached the brain and musculature they are not susceptible to anthelmintic agents.