Despite considerable research examining insight in patients with psychoses, non-psychotic disorders and chronic organic brain syndromes, results are inconclusive and insight remains a source of some mystification. To what extent can patients understand disorders which affect their mental function? Does insight bear a prognostic value? Is impaired insight determined by the illness or are other factors of equal importance? Ivana S. Marková examines the problems involved in studying insight in patients with mental illness in order to provide a clearer understanding of the factors that determine its clinical manifestation.