Proteins from leaf, seed, fruit and vegetable clarified homogenates were first separated in native polyacrylamide gels specific for basic proteins. They were then transferred to an overlay gel containing Micrococcus cells as substrate for detection of lysozyme activity. Extracts from 410 plant species representing 116 families were tested and lysozyme activity was found in 168 species from 71 families. One to five electrophoretic forms of lysozyme activity were observed. The relative electrophoretic mobility and intensity of each isoform was compared with known amounts of hen egg white lysozyme as reference lysozyme. This is the first report of the presence of lysozyme activity in gymnosperms and lower plants. In 20μl extracts, isoforms with activity corresponding to more than 10 μg of purified hen egg white lysozyme were found in Lychnis chaledonica, Phaseolus coccineus, Petroselinum crispum, Phytolacca americana, Adonis vernalis, Dictamus albus and Hyoscyamus niger leaf extracts, and Rumex acetosa and Punica granatum seed extracts. © 1990.