Abstract: Terentang (Campnosperma brevipetiolatum Volkens) stem bark contains alkaloids, saponins, tannins, and flavonoids that can nourish hair and blacken and clean hair. This study aimed to determine male rabbits' hair growth activity from terentang stem bark extract and the most effective concentration in hair growth. This study used 6 treatments, namely: no treatment, negative control (aqua dest), positive control (Regrou), and terentang stem bark extract with a concentration of 0.5%, 1%, and 5%. Treatment was carried out every day with an application volume of 1 ml for 21 days. Hair length measurements were carried out on the 7th, 14th, and 21st days. Hair weight measurements were carried out on the 22nd day. Data obtained were processed statistically with the one-way ANOVA method. The results of one-way ANOVA statistical analysis showed significant differences in hair growth activity in each treatment with a value of P=<0.00 (P<0.05). Based on the results, it can be concluded that terentang stem bark extract with a concentration of 5% was the most effective concentration in growing hair of male rabbits.