FOR THE INITIAL PERIOD OF THE DRUG ABUSE WARNING NETWORK (DAWN I), MORE THAN 1000 DIFFERENT SUBSTANCES WERE REPORTED, AND THE 50 MOST FREQUENTLY CITED DRUGS ACCOUNTED FOR 89 PERCENT OF THE MORE THAN 35,000 MULTI-DRUG REPORTS. THE LARGEST PHARMACOLOGICAL CLASS AMONG THEM WAS DEPRESSANTS. ANALYSES INDICATED THAT THE PROPORTION OF MULTI-DRUG MENTIONED AMONG THESE SUBSTANCES WAS NEGATIVELY CORRELATED WITH RELATIVE FREQUENCY OF ABUSE. THE AVERAGE AGE OF ABUSERS AND THE SEVERITY OF MULTI-DRUG INCIDENTS TENDED TO INCREASE PROGRESSIVELY WITH THE NUMBER OF DRUGS INVOLVED. THE GREATER NUMBERS OF DRUGS TENDED TO INVOLVE PROGRESSIVELY GREATER PROPORTIONS OF WHITES THAN BLACKS, BUT NOT GENERALLY GREATER PROPORTIONS OF MALES THAN FEMALES. SUCH DEMOGRAPHIC PATTERNS WERE ALSO COMPARED FOR SPECIFIC DRUGS IN PROGRESSIVELY LARGER MULTI-DRUG COMBINATIONS. IMPLICATIONS OF THE METHODOLOGIES ARE DISCUSSED FOR VALIDATION OF THESE RELATIONS AND FOR EVALUATION OF LONG-TERM TRENDS IN ABUSE PATTERNS. (AUTHOR ABSTRACT)...MSP