Life-tables and tables of age-specific fecundity were constructed for the sawtoothed grain beetle,Oryzaephilus surinamensis(L.), and the merchant grain beetle,O. mercator(Fauvel), at a temperature of 30°C and relative humidities of 12, 33, 56, and 74%. These tables were used to calculate the gross rate of reproduction, the net rate of reproduction, the innate capacity for increase, the finite rate of increase, and the generation time. The results indicated that in both species the rate of population growth increases rapidly with humidity between 12 and 56% RH and then remains nearly constant up to at least 74% RH. Neither species was able to complete development at 96% RH.