There are few prospective studies investigating the effectiveness of educational programs on osteoporosis knowledge in young women.  Ten sections of a college physical activity course were randomized to either a short osteoporosis education intervention or control group.  Osteoporosis knowledge (risk factors) was determined at baseline, and at day 7 (post test 1) and day 21 (post test 2) following intervention using the Multiple Osteoporosis Prevention Survey.  The intervention consisted of the National Osteoporosis Foundation's fully scripted power point presentation, “Osteoporosis: The Silent Disease” supplemented with a “Risk Factor Card: Can It Happen To You?” and an educational pamphlet “Osteoporosis: What You Need To Know.”  Chi-square and ANOVA evaluated for between group differences.  We hypothesized that each outcome variable would be favorably influenced by the intervention.  Alpha was set at 0.05.  There were no between group differences at baseline for the study variables.  Thirty-nine out of 56 (69.6%) intervention women and 63 out of 77 (81.8%) control women completed all study requirements (102 out of 133, 76.6%).  Ninety two percent were white and 90% ranged in age from 18 to 21 years.  The percentage of all women who correctly identified osteoporosis risk factors was high for low calcium intake (97.1%), family history (96.1%), sedentary (95.1%), female (78.4%), scoliosis (76.5%), and post menopause (76.5%) while it was poor for smoking (59.8%), steroid or thyroid medications (55.9%), skipped menstruation (44.1%), early menopause (49.0%), small, thin frame (48.0%), alcohol use (47.1%), white race (27.5%) and Asian race (8.8%).  A significantly higher percentage of intervention women identified correctly 8 out of 14 risk factors at post test 1 and this difference was maintained at post test 2 for small, thin frame (94.9% vs. 68.3%; X²=10.08; P=.001), alcohol use (87.2% vs. 54.0%; X²=11.95; P=.001), smoking (87.2% vs. 58.7%; X²=9.21; P=.002), white race (71.8% vs. 28.6%; X²=18.17; P<.001), and Asian race (41.0% vs. 14.3%; X²=9.30; P<.002).  The sum score of identifying correctly 14 risk factors was similar at baseline between intervention and control (mean 8.69±2.47 vs. 8.54±2.33; F=0.98; P=.754) but was significantly different at post test 1 (mean 11.64±2.54 vs. 8.70±2.58; F=31.49; P<.001) and post test 2 (mean 11.56±2.63 vs. 9.43±2.43; F=17.40; P<.0001).   A short osteoporosis education program using professionally developed and publicly available material was effective in improving and maintaining young women's ability to correctly identify osteoporosis risk factors.  Knowledge was increased in areas which at baseline were determined to be at a poor level.