DR1 has been known as a well defined antigen since the Seventh International Histocompatibility Workshop (1). At the Ninth Workshop the antigen frequency was determined to be 14.7% in Caucasians and 9.45% in Negroids (2). The DRwlO antigen was described by Jakobsen et al. in 1979 (3), then reporting a new DR antigen associated with B37. In the Ninth Workshop (2), the frequency was found to be 2.1% in Caucasians and 3.5% in Negroes. At the Third Asia-Oceania Workshop, this antigen was found to be especially frequent in the AsianIndian populations (up to 10%). Recent biochemical and DNA sequence studies have provided evidence that the DR1 and the DRw10 β 1 chains are quite different (4).