Two lots of quebracho tanned leather and two lots of commercial leather were treated to contain varying percentages of sulphuric acid. One half of this leather was then aged at 65 percent relative humidity and the other half at 86 percent relative humidity. The tensile strength was measured at different aging periods and was calculated as percent of the original tensile strength. The leather deteriorated more rapidly at the higher humidity. The deterioration was greater for greater acid concentrations and for longer aging periods. -- CAL