Current clinical correlates of duration of initially untreated psychotic symptoms were investigated in a cross-sectional analysis followed by a 10-year prospective study among 88 in-patients with a long-standing schizophrenic illness, many of whom had experienced prolonged periods of untreated psychosis due to illness onset and hospital admission in the pre-neuroleptic era. After controlling for the effects of age, and duration and continuity of subsequent neuroleptic treatment, the primary clinical correlate of duration of initially untreated psychosis was muteness. Over the subsequent 10-year-period, no new cases of muteness emerged and some existing cases of muteness partially resolved, though the speech that emerged remained very sparse and revealed generally gross cognitive debility. The pathophysiology underlying active, unchecked psychosis may also constitute an active morbid process that is associated with the further progression of severe negative symptoms and cognitive dysfunction in the long-term.