For many years it has been the policy of the London Authority to avoid the certification of patients directly from their own homes, by passing them through an observation ward before making a decision as to their disposal. The system originated partly from the fact that the London Mental Hospitals are some distance from town, and partly from the shortage of accommodation, it being necessary to secure the safe custody of the patients pending their admission. The small scattered wards have now been fused together to form larger and more efficient units, which ensure every case having the fullest consideration and investigation before deciding upon any method of disposal. The various points arising in this paper are illustrated by reference to the work of the largest of these units.