This two-part preliminary study assessed the effects of various cardiovascular exercise session frequencies and durations on depression and tension score (Profile of Mood States-Short Form) changes over 10 weeks with previously sedentary, apparently healthy adults who were new members of 2 southeastern U.S. community wellness/fitness centers. Experiment 1 (M age = 32.6 years, SD = 7.9) demonstrated significant (p <.05) reductions on both depression and tension scores for the medium (16-22 sessions, n = 26) and high (24-30 sessions, n = 24) frequency groups, while the low frequency group (10-15 sessions, n= 22) had a significant reduction only on tension. No significant changes were found for the wait list control group (n = 26). ANOVAs with Scheffé follow-up comparisons indicated significantly greater reduction on depression and tension scores for the high and medium frequency groups. Experiment 2 (M age = 32.1 years, SD = 7.7) demonstrated significant (p <.05) reductions in tension scores for groups completing 15-min (n = 20) and 30-min (n = 20) exercise sessions, but not for the no exercise control group (n = 18). Only the group completing 30 min of exercise demonstrated significant change on depression. ANOVAs with follow-ups indicated no significant differences in reduction on either psychological measure, between either exercise condition. The study provided data that may lead to determining lower end exercise frequency and duration "thresholds" for significant depression and tension reductions. Limitations, the need for replication, and practical implications are discussed. © 2003 by Human Kinetics Publishers and the European College of Sport Science.