The present study is concerned with the outcome of long‐germ lithium maintenance therapy administered to 107 manic‐depressive patients after more than 12 months. Nine patients failed to respond despite having met the criteria for maintenance within the therapeutic range of lithium. This group, termed “lithium non‐responders”, had all shown bipolar illness with gross morbidity with frequent cycles,>4 per year, seven had a family history of affective illness (six bipolar). The study did not demonstrate any other clear factors common to the “non‐resp