After 14 days, the patients will be classified as responders or non-responders. A responder is defined by a reduction of the initial HAM-D score of more than 50%. Study treatment will be stopped in non-responders and continued in a double-blind manner in responders for further 60 days. Thereafter, the the study medication is stopped and the patients are observed for further 14 days. Study visits will be performed every 14 days. This extension phase was added to examine if a prolonged treatment with olanzapine could ensure a sustained treatment effect. It should be excluded that olanzapine has a short-term tranquillizer-like effect or leads to unfavourable medium- to-long-term depressiogenic effects as observed with other neuroleptics used in depression ( e.g. fluspirilene). Moreover, withdrawal effects should be excluded.