Electro-focusing combined with the PAGE method of electrophoresis was used to study variations in esterase isozymes among the four recognised species of Apis (A. mellifera, A. cerana, A. dorsata, A. florea) and two putative species (A. laboriosa, A.andreniformis), samples in tropical rainforest in Yunnan province, China. Eight other genera (one species of each) of Apoidea were also sampled. wie variation was found between genera, with most bands occurring between pH 4 and pH 8, and there were distinct differences between Apis species, although all bands fell within the pH range 5 - 6. It was possible to differentiate between the A. dorsata and A. laboriosa, which are similar morphologically, and between A. andreniformis and A. florea which likewise resemble each other closely.