This is a concise presentation of the phenomenological approach to the problem of delusion. Following Jaspers, the author classifies the various delusions according to the subjective experiences associated with them. Their clinical significance is discussed. The author goes beyond phenomenology in expressing the view that the delusions in depressive illness uncover man's primordial anxieties. But he believes that paranoid delusions cannot be fully explained psychologically. He does not think that existential analysis can make a major contribution to the elucidation of the problem.