Pulmonary oedema is a common sign of East Coast fever (ECF, Theileria parva infection) of cattle. A trial was conducted on farms in Uganda to compare a product containing both the antitheilerial compound parvaquone and the diuretic compound frusemide with one containing only parvaquone, in the treatment of ECF. The trial involved 40 clinical cases of ECF, some of them complicated by other infections, in cattle of all ages and on several farms. Confirmed cases were treated with either parvaquone+frusemide (P+F) or parvaquone alone (P). Survival after treatment with P+F was 77% compared with 71% with P. Five of the 10 fatalities were complicated cases. The cure rate for severe but uncomplicated ECF was 89% with P+F and 40% with P. Pulmonary signs were resolved within 24-48 h after treatment with P+F and clinical recovery was noticeably more rapid than with P. The antiparasitic effect of the two treatments was similar. P+F could be particularly useful when reporting, diagnosis or laboratory confirmation of ECF is delayed, because advanced cases are more likely to be encountered under these circumstances.