The stability of entomopathogenic fungi is discussed, using examples from the literature on the effect of various environmental factors on growth and survival of fungi. Emphasis is placed on literature published since 1962. Light is usually detrimental to spore survival, but effects on other stages are varied. High temperatures produce mortality in vegetative stages of entomopathogenic fungi, but spores are much more heat resistant. Spore viability, however, is lost more slowly at low than at high temperatures. The surface upon which fungal spores are located will influence survival. Stability differences among substrates soil, water and host are discussed. High humidities are essential to spore germination, but the effect of high humidities upon disease development is unclear. Finally, the influence of various chemicals upon entomogenous fungi is reviewed.