The failure rate in long-term lithium treatment of bipolar affective disorder is in the range of 20 to 30%, even with rigorous diagnostic criteria an adequate serum lithium levels. This may be due to a variety of biologic and psychosocial factors. Psychosocial factors affecting treatment outcome were studied in 60 RDC diagnosed bipolar patients treated with lithium for one year. Outcome was measured using an affective episode score, a social adjustment scale and a global assessment scale. Social support was the factor most strongly correlated with a good outcome on all three measures.