A technique is described which facilitates analysis of the development of individual protoperithecia in Neurospora crassa. The formation of this organelle proceeds in several clearly discernible steps beginning with the looping of a single hyphal filament and ending with a heavily pigmented, densely packed structure that is the mature protoperithecial structure. The effects of a number of environmental conditions on the development of protoperithecia in two wild types and in a female-sterile mutant strain, ty-1. are presented.