Gross and microscopic changes in response to single po. doses of avicide 3-chloro-4-methyl benzamine HCl were studied in rooks (Corvus frugilegus L.) and pheasants (Phasianus colchicus L.). The observed changes followed a dose- and survival time related pattern and rooks were considerable more susceptible than pheasants to the toxicity of the compound. No effect was found in rooks and pheasants which survived safely 0.7 to 1.0 and 7.0 to 10.0 mg/kg doses, respectively. Early acute effect, in rooks died from 7.0 to 16.0 mg/kg within 16 to 18 h, included: congestion of the major organs, fatty degeneration of the liver, and extensive parenchymal degeneration of the kidney, particularly the proximal tubular epithelial cells. Progressive late effect developed in rooks and pheasants at 2.2 to 5.0 and 16.0 to 120.0 mg/kg doses, respectively, which died in coma between 32 to 80 h. It was characterized by a grayish white, frost-like material of uric acid overlaying the serosal surfaces of the various organs, accompanied by sterile inflammation and necrosis in the affected and adjacent tissues. Few urate deposition was also seen in some of the kidneys. Infrequently, interstitial pneumonia did also occur. The lesions produced by the toxic effect of the test compound seemed to be analogous to that of avian visceral gout.