This paper describes a prospective study of the relationship between non-psychotic prodromal symptoms and psychotic symptoms in 55 schizophrenic (DSM-III-R) out-patients. Once a month, a number of non-psychotic symptoms generally regarded as prodromal symptoms in schizophrenia were assessed, as well as psychotic symptoms, with standardised self-administered instruments and rating scales for a minimum of 12 months (range 12-29). The data were analysed for each patient using a longitudinal correlational design with a 1-month lag between the prodromal and psychotic symptoms over the total period. Results showed that in less than one-fifth of subjects did any of the prodromal symptoms, individually or in combination, show a significantly positive correlation with the subsequent level of psychotic symptoms. Such relationships were significant in an even smaller proportion of subjects when the confounding effect of concurrent psychotic symptoms on prodromal symptoms was partialled out. High levels of prodromal symptoms appeared to have adequate specificity but low sensitivity in their power to predict high levels of subsequent psychotic symptoms. There were no differences in age, gender, medication levels, and the number of previous admissions between the subjects who did or did not show a relationship between putative prodromal symptoms and psychotic symptoms.