The purpose of this study was to compare the physiologic effects of a program of combined running and weight training (RUN-CWT) with a program of circuit weight training (CWT). Thirty-six females (X age = 35.7 yr) and 41 males (X age = 36.1 yr) were randomly assigned to RUN-CWT, CWT, and control groups. The training groups participated in 12-wk programs, 3 d . wk-1. Three circuits of 10 weight-training exercises were completed with 12-15 repetitions performed in 30 s at 40% of one-repetition maximum at each station. The 30-min RUN-CWT program included 30 s of running on an indoor track following each CWT station, whereas the 22.5 min CWT program included a 15-s rest period between stations. The RUN-CWT groups had a significant (+ 17%) increase in VO2max (females 30.5-35.7 ml . kg-1 . min-1 and males 39.7-46.3 ml . kg-1 . min-1) and strength (females + 24% and males +21%), and a significant decrease in body fat percentage (females -3.2% and males -4.1%). The CWT groups also increased significantly in VO2max (+12%) and strength (+17%) and decreased in body fat (-3.0%). The controls did not change significantly in any variable. Statistically, one training program was not shown to be superior to the other; thus, both programs of RUN-CWT and CWT were effective in improving measures of physical fitness.