Quadrula metanevra were collected monthly from Pickwick Dam tailwater (Tennessee River mile 201.3), Tennessee, between July 1988 and June 1990. A total of 227 specimens were examined. The population consisted primarily of dioecious individuals (98%) and had an unequal sex ratio (1.5 female: 1 male). Histological examinations showed that typical spermatogenesis began in autumn (September), increased in spring (March–April), and continued until midsummer (July). Atypical spermatogenesis predominated during July and August, and may have increased the number of sperm produced in autumn and winter. Oogenesis followed a pattern similar to that of typical spermatogenesis, with smallest average oocyte size observed in August. Gamete release occurred between late winter-early spring (March) and midsummer (July). Brooding females were found between late March and July.