The effects of humidity during aging on autoxidation and detergency of sebum on clothes were studied. Refined lard was used as a test medel of sebum, and cotton and polyester fabrics were used as test fabrics. Test fabrics soiled with lard were hung for a fixed period in an incubator where temperature and relative humidity were controlled at 40℃ and 50 or 90%. Autoxidation of lard extracted from fabrics was estimated from the peroxide value (PV) and the carbonyl value (CV). The results were as follows: 1) PV and CV of lard increased by aging. The rate of increase on polyester was higher than that on cotton. 2) The effect of humidity at 90% RH on autoxidation of lard on cotton was greater than that at 50% RH, but there was no difference on polyester. 3) While about 30% of the lard adhered to cotton was removed by washing before aging, the removal rate of lard decreased to 0% after a 5-day aging period at 90% RH or a 20-day aging period at 50% RH. In the case of polyester, the removal rate was very low, irrespective of aging periods and humidity.