A short-term selection experiment was conducted with ICR albino mice produced by the reciprocal crossing of two lines of unselected animals which had been random-bred for 28 generations. Lines were developed by selecting for maximum and minimum serum cholesterol (SC) (lines CH and CL), voluntary physical activity (lines AH and AL), 56-day body weight (lines WH and WL) and feed intake (lines IH and IL). An unselected, random-bred control line was maintained with each pair of divergent selected lines (CC, AC, NC and IC, respectively). In the lines selected for SC, physical activity and 56-day body weight, selection was based on individual performance. Twenty-five paired matings plus five extra paired matings were used to perpetuate the lines each generation for five generations. The feed intake lines were perpetuated by within-sex, full-sib family selection with 30 paired matings per generation for five generations. / Ph. D.