Seventy per cent attempts to ensure interspecific hybridization between Poecilia velifera and P. sphenops were successful and led to the production of true hybrids, but not gynogens or triploids, as evidenced by the mottled or striped colour, chromosome number (2n = 46) and response from scale transplantation. Most hyrbids were infertile as they failed to cross among themselves or with their respective parents; however they were more closely related to P. sphenops as indicated by mating responses and scale transplantation studies. Heterospecific impregnation resulted in 40% reduction in fecundity but retention of interparturition period characteristic of the female species. A skewed ratio of 3 Female Female:2 Male Male, observed in the laboratory populations of both P. velifera and P. sphenops, was also sustained among the progenies sired from heterospecifically inseminated females. The colour patterns of hybrids were of two types: mottled and striped, the latter one being reported for the first time.