The effects of environmental factors on components of the life cycle of Puccinia menthae on Mentha × piperita cv. Tod’s Mitcham were examined. Urediniospore germination required at least 6 h leaf wetness and lasted 4-6 h at temperatures of 5-25ºC. Appressoria, substomatal vesicles, and haustoria were produced 6, 6, and 24 h after inoculation, respectively, at 20ºC. The latent period of infection ranged from 50 days at 5ºC to 10 days at 22ºC. Sporulation occurred over a wide range of temperatures (5-27ºC), the optimum being 15-20ºC. The minimum, optimum, and maximum temperatures for infection were <5, 20, and 27ºC, respectively. Teliospore formation required a minimum of 9 days of cold treatment (4ºC) and the ratio of teliospores to urediniospores produced was inversely proportional to the duration and intensity of light received.