When Otto Fenichel died suddenly at age 48, Anna Freud mourned the loss of "his inexhaustible knowledge of psychoanalysis and his inimitable way of organizing and presenting his facts." These qualities shine in his classic text, which has been a beacon to generations of psychoanalysts. Investigating the relationship between biological needs and external influences—the tensions and inhibitions that nurture neuroses—Fenichel concludes that "neuroses are social diseases," arising from the demands of civilization on the developing organism. For this 50th anniversary edition, distinguished psychoanalyst Leo Rangell has written an introduction to set the context of Fenichel's work and an epilogue to describe its influence.