SummaryIndex selection (I) was compared with independent culling levels (N) in ten replicates of a single generation selection experiment. Two correlated traits, egg laying between 7 and 11 days after adult emergence and adult weight at 12 days, were selected in Tribolium castaneum. Selection criteria included family means for egg laying and individual phenotypic values for adult weight. The response to index selection was greater than the response to independent culling levels for the aggregate genotype (8.80, 4.38) and the difference was highly significant (P < .001). The predicted response to independent culling levels was slightly less than that for index selection for the aggregate genotype. The very large difference found in the index line relative to culling level line could be due to the fact that family selection was used for egg laying. Responses obtained for both individual traits were also greater in the selection index line, and the difference was significant (P < .001) for egg laying (8.13, 3.96) but not for adult weight (0.67, 0.42). A greater response would be expected in the selection index line for each individual trait when optimum culling proportions are used in the culling levels line. Independent culling levels should be considered in practice as a relatively simple but inefficient selection method to improve egg laying and adult weight.