Two-dimensional gel electrophoresis was used to analyse stage-specific proteins from Phytophthora palmivora, a pathogen of cocoa and other economically important tropical crops. Approximately 1% of proteins appeared to be specific for each of the mycelial, sporangial, zoospore, cyst and germinated cyst stages of the life-cycle. Three proteins excised from protein gels of P. palmivora were identified as isoforms of actin by database searches to public libraries of Phytophthora infestans. The protein profiles of parallel samples of P. palmivora and P. infestans demonstrated that 30% of proteins precisely co-migrated suggesting that proteomics may be used to examine changes in the specific stages in the life cycles of Phytophthora spp.