Lantana toxicity of guinea pigs elicited an increase in hematocrit, erythrocyte and leukocyte number, hemoglobin, urea-nitrogen and bilirubin contents in the blood of the affected animals. Most of the bilirubin was present in the conjugated form. Enzyme activities of glutamic oxaloacetic transaminase, acid phosphatase, lactate dehydrogenase, glutamate dehydrogenase, sorbitol dehydrogenase in the blood plasma of affected animals exhibited a marked increase. Acid phosphatase activity was inhibited by tartrate. Enzyme activity of alkaline phosphatase remained unchanged while that of glutamic pyruvic transaminase showed a marginal decrease.