The purpose of this study was to determine if the penetration enhancer SEPATM (2-n-nonyl-1,3-dioxolane) would augment the scalp hair growth effects of topical minoxidil in the balding stumptail macaque. A 1-in2 area on the balding scalp of 40 adult female monkeys (four drug-treated and four vehicle-treated groups of 5 monkeys each) was topically treated 5 days/week, q.d. or b.i.d., with approximately 250 μl of minoxidil-SEPATM (2.5% minoxidil, weight/volume in 10% SEPATM, 25% propylene glycol and 65% isopropyl alcohol), Rogaine® topical solution (TS, 2% minoxidil, weight/volume in 20% propylene glycol, 60% ethanol and 20% water) or respective vehicles (without drug) for 16 weeks via paintbrush application. Scalp hair was collected by shaving and vacuuming the dosed area at baseline and at 4-week intervals. The shaved hair was filtered, weighed and recorded as the change from baseline. The q.d. and b.i.d. minoxidil-SEPATM groups displayed a significant increase in hair weight compared to their respective vehicles at week 4 whereas q.d. and b.i.d. Rogaine® TS groups were not active until week 8 and 12, respectively. Both minoxidil-SEPATM treatments produced significantly greater cumulative hair weight over the entire 16-week study compared to either of the Rogaine® TS treatments. Comparable increases in cumulative hair weight were evident between q.d. and b.i.d. minoxidil-SEPATM groups and between q.d. and b.i.d. Rogaine® TS groups. Twenty-four-hour urine samples were collected at steady state to assess urinary excretion of total minoxidil via high performance liquid chromatography analysis in each of the four drug-treated groups. Urinary levels of total minoxidil tended to be greater in minoxidil-SEPATM groups. However, due to high intragroup variation, only the b.i.d. minoxidil-SEPATM group showed a significant 2.8-fold elevation compared to the b.i.d. Rogaine® TS group. These data suggest that the penetration enhancer SEPATM influences the topical delivery of minoxidil resulting in earlier and greater stimulation of scalp hair growth in the balding stumptail macaque.