This report presents interim results from a series of studies of the lumbosacral region of the spine. A new classification of the lumbosacral transitional vertebra (LSTV) is proposed. An LSTV was found with similar frequency in patients and in population samples. The radiological findings were related to the presence of symptoms and to evidence of urological problems. Whilst Brocher (1973), Rubin (1971), and others have considered an LSTV to be of importance because it should lead to unfavourable weight bearing in the lower spine, the present extensive material shows that there is no relation between an LSTV and low backache. There may be a genetic factor involved in the various types of LSTV.