The median and maximum life spans of Zaprionus paravittiger at 26 +/- 2 degrees C were 35.45 +/- 0.39 and 70.0 +/- 1.00 days, respectively, in males and 39.93 +/- 0.40 and 77.67 +/- 0.58 days in females. Feeding of an antioxidant-sodium hypophoshite (SHP), 1, 10 1 X 10(2) and 1 X 10(3) microM-resulted in increased survival of both sexes. Further increase in SHP concentration accelerated the mortality rate. Secondly, the lipid peroxide level as measured by malondialdehyde content showed an age-related increase in normal as well as SHP-fed cohorts. However, the rate of increase was much slower in the latter. It is suggested that SHP, by virtue of its free-radical scavenging property, prolongs the life span of Z. paravittiger.