Dermatan sulfate with a high iduronate content may be precipitated selectively from solution with lead acetate at neutral pH. Other glycosaminoglycans, including dermatan sulfate with appreciable glucuronate content, are in general not precipitated. Both dermatan sulfate and mucokeratan sulfate are precipitable by the alkaline copper procedure, so that prior removal by lead acetate of some or all of the dermatan sulfate from a mixture of glycosaminoglycans permits concentration of mucokeratan sulfate. This eases considerably the detection and isolation of this recently identified glycosaminoglycan.