1. A 99-item questionnaire is introduced to estimate the extent and dimensions of emotional immaturity or dysplasia in psychiatric patients. It is shown to be validly differentiating with respect to 260 healthy controls and 363 psychiatric patients classified in 6 diagnostic groups. Eighteen dimensions of the concept were tested and of these 13 proved to be statistically significant.2. Chronological age and sex were found to be critical variables in addition to diagnosis and facilitated the extraction of an emotional maturity quotient, the "E.M.Q." Emotional immaturity lessens significantly with advancing years in all groups save schizophrenia and epilepsy but the growth potential is less for mentally sick patients than for the healthy controls.3. The raw E.I. Scores and E.M.Q. showed a positive significant interdependance with "neuroticism" and with morphological growth estimates but a slight negative correlation with an I.Q. test.Abstract Teaser