1. Extract of psidium guajava root induced sex organ atrophy in male rats and diestrus in the female by subcutaneous injection. Growth retardation, adrenal hypertrophy, thymus involution and local necrosis were observed also.
2. No remarkable change was found in the orally administered rats.
3. Vacuolated basophils were found in the anterior pituitaries of the injected rats, especially many in the male.
4. Oestrous cycle of mice was inhibited by oral administration. of large amount of psidium extract. Slight decrease of the weight of the prostate with seminal vesicles was observed in male young mice but it is not statistically significant.