The toxicity of 5 Sudanese plants credited with medicinal value for man, i.e. Citrullus colocynthis, Jatropha aceroides, J. glauca, Solanum dubium and Lagenaria siceraria, was studied by giving the dried or minced plants to Nubian goats, Desert sheep or Zebu calves by mouth or stomach tube. The clinical, haematological and pathological changes indicated that all five plants reduced the ability of the liver to synthesize protein, although there was no evidence of interference with the excretion of bilirubin. Kidney dysfunction and haemoconcentration also occurred. Citrullus colocynthis and Jatropha species in doses of 0.5 to 10 g per kg per day killed goats after dosing for periods ranging from 1 day to 2 weeks. Calves were less susceptible. The fruits and leaves of L. siceraria, in doses of 1 to 5 g per kg per day, caused death after a similar period but with less regularity. The seeds were less toxic. The fruits of S. dubium in doses of 2.5 to 10 g per kg per day killed goats in 2 to 5 days. Similar doses of the leaves caused deaths in 8 to 36 days. In sheep, both fruits and leaves required a longer period of dosing to cause death.