THE PURPOSE of the Registry on Blood Dyscrasias is: ( 1 ) to alert physicians to the potential hematopoietic toxicity of new drugs; (2) to remind physicians of the potential toxicity of other drugs; and (3) to serve as a reference for physicians who are investigating patients suspected of having drug-induced blood dyscrasias. The Council on Drugs recommended establishment of the Registry in 1953. After a preliminary attempt and a pilot study, it was placed on a permanent basis in 1957. Since 1959, a systematic attempt has been made to include reports abstracted from the foreign literature, in addition to those received from other sources. Cumulative tabulations of all reports have been made semi-annually since 1957, and are distributed to interested individuals and institutions. For the past 2 years, separate resumes based on these tabulations have been prepared to indicate trends and point out drugs added to the Registry during the preceding