Single larval inoculations of both the citrus and banana races of Radopholus similis from Florida indicate parthenogenetic reproduction is possible. These races normally reproduce amphimictieally. Both races produced all-female populations from single larva inoculations after 80 d and male-female populations after 180 d. The all-female populations produced female progeny with viable eggs, but no spermatozoa were present in the spermatheca, indicating tychoparthenogenesis occurred. Uninseminated females in the latter study produced both male and female progeny. Approximately 95% of the female progeny of the male-female populations were inseminated, indicating that cross-fertilization had occurred. The proportion of males to females was as expected in a normal bisexual population. No intersex males were observed. The mechanism of sex determination is not fully understood but assumed to be enviromnentally induced.