We review the concept of endogenous depression historically and undertake quantitative analyses of representative factor analytic studies. We also report an empirical study, isolating symptoms and signs associated with a clinical diagnosis of psychotic/endogenous depression, made by a large number of clinical raters assessing 300 depressives. The quantitative analyses and the study of practising psychiatrists agreed in delineating depressive type and together suggest a more restricted construct of endogenous and psychotic depression than has been held historically. Key clinical features isolated were severity, retardation, delusions and paranoid features, non-reactivity and non-variability in mood, while vegetative features appeared to lack relevance.