Fifty-eight different populations of Rotylenchulus reniformis were recovered from soil and root samples of different crops and inoculated in cotton (Gossypium hirsutum) cv. COODETEC 402 and castor bean (Ricinus communis) in clay pots in the greenhouse at the Departamento de Fitossanidade of the Universidade Estadual Paulista, Jaboticabal Campus, São Paulo State, Brazil. Using a light microscope, a comparative morphometric study was carried out which included a multivariate analysis of all the populations. Eleven morphometric and seven derived variables were evaluated in ten young females of each population. The range of morphometric values and variables in the Brazilian populations of this nematode such as length of the t, V and tail shape are wider than in populations of the same species from others regions of the world. The data confirmed that the length of the t, presence of males and V are sufficient for identification of R. reniformis. This also is the predominated species of the group found in Brazilian agro-ecosystems.