What conclusions may reasonably be drawn from this limited consideration of acute lumbago? As in all other aspects of medicine accurate diagnosis is essential. The possibility of sacro-iliac injury should always be remembered as it is much commoner than is usually supposed, even in cases closely resembling simple fibrositic lumbago. Fibrositis frequently follows improperly treated sacro -iliac strain or injury and often accompanies it, so its presence is in no way to be regarded as a conclusive diagnosis. Indeed a diagnosis of fibrositis in this area should only be arrived at when all other causes of acute low back pain have been excluded. Attention is drawn to the great value of manipulative treatment in certain types of fibrositic lumbago, in cases where muscle injury is present, and in cases termed diffuse fibrositic lumbago (where a pre-fibrositic condition is postulated) . For convenience of treatment cases formerly termed acute myalgia are included in this latter group. An attempt is made to explain the rationale of manipulative treatment which is considered - in cases suitable for its use - to produce the same therapeutic effects as skilled massage, and the various forms of heat application, but in a more rapid and dramatic manner. The usual aetiolocical factors must be sought and eliminated if present. For the adequate treatment of present and the prevention of future attacks great ennhasis is laid on what have been termed postural defects and on other factors having unfavoura`- le effects in the dynamics of the skeleton. Such matters as dietary faults and unsuitable and dangerous systems of exercises come under review.