This research has compared the levels of some biochemical and lipid perooxidation parameters between the Dirofilaria immitis infected and ivermectin treated dogs. The dogs of the experimental group were treated with 0.05 mg kg(-1) ivermectin and blood samples were colelcted on the 7th day after treatment. The blood samples were analyzed for microfilariae (mf) concentration and the plasma samples were analyzed for MDA and NO levels, serum ALP, ALT, AST, CHOL, GGT, total protein and triglyceride levels on day 0 and 7. The results of this study showed that the MDA and NO levels of the dogs naturally infected with D.immitis were higher than those of the control group. It was also demonstrated thta ivermectin treatment is effective on D.iimitis microfilariae. Consequently, heartworm disease causes lipid peroxidation in dogs but ivermectin treatment possesses no regulatory effects on serum biochemical parameters, except for NO and AST.