Program objectives are accomplished by making undercover heroin purchases and analyzing them for price, purity, adulterants/diluents, and geographic source area. Results are then reported to Federal, State, and local authorities. During July-September 1992, the DMP collected heroin samples in 18 metropolitan areas throughout the United States. Of 114 exhibits purchased, 82 percent contained heroin. Thirteen exhibits (17 percent) were from Southeast Asia and had an average purity of 37 percent; 26 exhibits (34 percent) were from Southwest Asia and had an average purity of 59.3 percent; and 38 exhibits (49 percent) were from Mexico and had an average purity of 26.5 percent. Sixteen exhibits that could not be classified as to origin had an average purity of 35.3 percent. Average cost per milligram of pure heroin by source area was as follows: Southeast Asia, $1.36; Southwest Asia, $0.86; and Mexico, $1.66. Appendixes contain data on individual city sampling