SUMMARYTwo field trials of fungicides for the control ofPhytophthora palmivoraon cocoa in Nigeria are described. The results obtained during two harvest periods have been subjected to two methods of analysis and are compared and discussed. The field results have been correlated with the results of laboratory bio‐assays and a close agreement is demonstrated. Possible reasons for the poor control ofP. palmivorain the field trials are considered in the light of results obtained from laboratory tests of fungicides (Hislop&Park, 1962a, b