Cotton fabric was dyed with indigo at different pHs, dye concentrations, and repeated dyeings. And the K/S value and dye uptake of the dyed materials at those conditions were determined. The decrease of pH during the reduction process of indigo stock solution was observed. As a result the decrease of pH of the dye stock solution depended on the dye concentration and initial pH. The highest K/S value was shown at fabric dyed at pH 11 and the relationship between K/S value and dye uptake depended on initial pH of reduction bath and the slope was lower as the pH increased to 13.