Culture of broccoli (cv. Green Mountain) anthers at elevated temperatures (e.g. 35°C for two days) prior to maintenance at 25°C stimulated microspore embryogenesis. Embryo yields were also increased by subjecting excised inflorescences to a short term, high temperature shock (i.e. 45°C for one hour followed by 40°C for three hours) prior to anther plating and by a ten-fold increase in the auxin level of the anther culture medium.