A toxin fraction was obtained from Lantana camara L (red variety) leaves by batch extraction and column chromatography on silica gel (60-120 mesh). The main constituents of the toxin preparation were lantadene A and lantadene B and it was devoid of reduced lantadene A. Oral administration (125 mg/kg bwt) of the toxin to male and female guinea pigs caused icterus and photosensitization within 48 hr. All the affected animals had hepatomegaly and significant increases in conjugated and unconjugated bilirubin in blood plasma. The intoxicated animals of either sex had marked increases in acid phosphatase activity which was inhibited 45.77% and 49.35% by 1 mM tartrate in male and female animals respectively. The corresponding inhibition of acid phosphatase activity in control male and female guinea pigs was 15.91% and 20.33% respectively.