ABSTRACTrn(A) LIDRISA MARDA (2006210107)rn(B) SOSOR BEBEK LEAF EXTRACT PEEL-OFF GEL MASK (Kalanchoe pinnata Pers.) PHYSICAL STABILITY AND ANTIOXIDANT ACTIVITY TESTSrn(C) ix + 118 pages; 27 tabels; 14 pictures; 27 attachmentsrn(D) Key word: Stability test, peel-off gel mask, sosor bebek leaf, antioxidant activity testrn(E) Sosor bebek leaf extract contains natural antioxidants such as Vitamin C and flavonoid which are very good for the skin as anti-aging substances. They play a role in collagen synthesis process and protect skin from free radicals. Sosor bebek leaf extract was made into peel-off gel mask form. In the research, two formulas were made: formula I with 10% PVA and 0,5% karbomer 940 base and formula II with 13% PVA and 5% PVP base. The gel mask was made with trituration method using homogenizer. The stability of the gel formed was tested for a month, stored at room temperature (25°C – 30°C) and 40°C/75% RH inside a climatic chamber. Test points were on week 0, 1, 2, 3, and 4 with evaluation covering homogeneity, organoleptic, viscosity and flow feature, spreadability, tensile strength, pH, and drying speed. The stability test reveals that peel-off gel mask formula II had stable physical at room temperature and 40°C/75% RH with viscosity of 19166,67-21333,33 cPs, Newton flow feature, spreadability 6,63-6,816 g.cm/s, pH 5,1, drying speed 17 minutes and 25 minutes and tensile strength 116,12 kg/cm2 and 95,28 kg/cm2. Antioxidant activity test on sosor bebek leaf extract shows that the extract was very active in inhibiting 50% free radicals, with 34,007 μg/mL IC50 and on gel mask 81,051 μg/mL IC50 at room temperature and 112.983 μg/mL IC50 at 40°C.rn(F) References: 31 pieces (1989-2012)rn(G) Dra. Kartiningsih, M.Si, Apt.rn(H) 2013