In male mice of the C57 strain, chlordiazepoxide (CDP) (2.5, 5.0 and 10.0 mg/kg) reduced the latency to begin eating and prolonged the total time devoted to eating in a food-preference test. The increase in feeding duration arose from an increase in the mean duration of individual eating episodes and not from a change in the number of episodes that were initiated. In contrast, in male mice of the A2G strain CDP (at the same dose levels) did not reduce the latency to begin eating and only prolonged the total time devoted to eating at a single dose level (5.0 mg/kg). The two strains differed in their choice between novel and familiar foods that were concurrently available in the test. The A2G mice virtually ignored the palatable novel foods and devoted all their feeding to the familiar food. The C57 strain, however, spent more time eating the novel foods than the familiar food. CDP at all doses increased the duration of feeding devoted to familiar food in the C57 animals, but did not increase feeding duration in the A2G mice. However, CDP (10.0 mg/kg) increased the time spent eating novel foods in both strains to the same degree. Possible mechanisms underlying the effect of CDP on food-preference behaviour in mice and accounting for the strain difference in response to CDP are considered.