For commercial use of the entomopathogenic nematodes Steinernema carpocapsae and Steinernema feltiae in biological control of insect pests, they are produced in liquid culture on artificial media pre-incubated with their symbiotic bacteria Xenorhabdus nematophila and Xenorhabdus bovienii, respectively. After 1 day of the bacterial culture, nematode dauer juveniles (DJs) are inoculated, which recover development. The adult nematodes produce DJ offspring, which are harvested and can be sprayed. This study determined optimal temperatures to obtain high DJ progeny within a short process time. Temperatures assessed were 23A degrees C, 25A degrees C, 27A degrees C, and 29A degrees C for S. carpocapsae and 20A degrees C, 23A degrees C, 25A degrees C, and 27A degrees C for S. feltiae. The recovery of inoculated DJs was hardly affected and was reduced only in S. carpocapsae at 29A degrees C. The fecundity (eggs in uterus) in S. carpocapsae reached a maximum at 27A degrees C; whereas, maximum yields were recorded at 25A degrees C. For both Steinernema spp., highest DJ densities were obtained after 15 days incubation at 25A degrees C. Optimal culture temperature for both nematode species is 25A degrees C. S. carpocapsae was more sensible to suboptimal temperature than S. feltiae. Results on total DJ density and DJ proportion of the total nematode population were more variable at non-optimal temperature condition for S. carpocapsae than for S. feltiae. Suboptimal culture temperature also reduced DJ infectivity.