The emotional and behavioral responses of methadone patients to HIV antibody testing were examined by comparing 8 seropositives with 8 matched seronegatives. Seropositives displayed a wide range of immediate emotional reactions to learning their results, but no severe or damaging reactions; seronegatives were uniformly relieved. Almost all patients informed other persons of their serostatus with unremarkable consequences. Seropositives had higher anxiety than seronegatives at the 3-month follow-up, but behavioral outcomes were similar, tending towards reduced AIDS risk. The sample's program retention rate one year later was 94%.