Although push-ups and sit-ups are among the most commonly used body-weight exercises to improve and assess strength and fitness, there is a lack of reproducible test protocols in the scientific literature. The aim of this study was to evaluate the test–retest reliability of sit-ups and push-ups and to determine performance differences in muscular endurance (maximal number of repetitions) and power (timed, maximal number of repetitions in 30 s) in young women and men. Thirty-eight women and 25 men, 18–35 years of age, participated in the study. Thirteen women participants performed two test sessions of each test using a test–retest design. A high reliability was noted for both the sit-up and the push-ups tests (intraclass correlation values ranged from 0.92 to 0.95). There were no significant differences between the men and the women in the mean number of sit-ups (42 and 41 repetitions respectively for endurance and 16 and 14 repetitions respectively for power), whereas the men performed significantly more push-ups than the women (39 and 17 repetitions respectively for endurance and 29 and 13 repetitions respectively for power). In conclusion, sit-ups and push-ups are tests with high reliability, which are easy to perform and may therefore be recommended for clinical use to evaluate muscular endurance and power in young men and women. Moreover, the fact that men performed twice as many push-ups as women indicates that, when designing training programme for women, attention should be turned towards strengthening exercises of the upper body.