In toxicologic testing or experimental studies using animals, an adequate knowledge of spontaneously occurring lesions is required. 144 male and 184 female untreated Syrian golden hamsters (strain Han:AURA) were kept for life under standard laboratory conditions and an investigation of non-neoplastic lesions in relationship to the lifespan was performed. The average lifespan of the males was 106 weeks and that of the female hamsters 97 weeks. While cartilage degeneration of the sternum and fatty degeneration of the femoral bone marrow occurred already in the first half of life with high incidence, the majority of lesions were observed in the second half. The most frequent non-neoplastic changes in various organs were fatty change, calcification, cystic change, hyperplasia and amyloidosis. Such spontaneous lesions were discussed in connection with the same alterations which can also be induced by chemical or hormonal agents.