The effect of 7 wk consumption of a diet containing 32.6% of kilocalories as fat [condensed milk (CM) diet] on body composition and energy intake was evaluated in nine strains of inbred mice (AKR/J, C57L/J, A/J, C3H/HeJ, DBA/2J, C57BL/6J, SJL/J, I/STN, and SWR/J). Control animals were fed a high-carbohydrate diet containing 11.6% of energy as fat (Purina Rodent Chow diet). Relative to Chow diet controls, the CM diet significantly increased carcass lipid content in six strains (AKR/J, C57L/J, A/J, C3H/HeJ, DBA/2J, and C57BL/6J), but had no or a marginal effect on adiposity in three strains of mice (SJL/J, I/STN, and SWR/J). The obesity produced by the CM diet in six strains was not due to hyperphagia. Only one of six (AKR/J) of the strains that increased adiposity on the CM diet consumed more energy than controls during the 7 wk of the experiment. The identification of inbred mouse strains that are sensitive to dietary obesity, vs. others that are resistant, provides a useful tool to pursue the metabolic and genetic basis of this trait in the mouse.