AimsThe aim of this study was to test the activity of seven Tolypocladium cylindrosporum isolates against different developmental stages of Aedes aegypti. Methods and ResultsOvicidal activity (30% of eclosion; at a 84% eclosion of control eggs) and lowest cumulative emergence of adults (30%; at a 663% control emergence) originating from eclosing larvae was found 15 and 30days, respectively, after applying conidia of ARSEF 962 or 1580 onto the eggs. All isolates induced larval mortality when third-instar larvae were treated with conidia (5% control mortality); the lowest lethal concentration (LC50) at 5days after treatment was found with ARSEF 1580 (92x10(5)conidiaml(-1)), and the shortest lethal time (LT50) with ARSEF 2912 (28days at 33x10(6)conidiaml(-1)). The pathogenicity of T.cylindrosporum to A.aegypti adults is corroborated. ARSEF 1027, 1580 and 2912 induced the highest cumulative mortality in adults (90%) 15days after application (5% control mortality). ConclusionsFindings emphasized an isolate- and developmental stage-related virulence of T.cylindrosporum. Significance and Impact of the StudyARSEF 1580, in the group of tested isolates, is the most promising isolate for use against terrestrial eggs, aquatic larvae and adults of this important vector.