Gender differences in premorbid adjustment, clinical presentation, and longitudinal course have been considered increasingly in explanatory models of psychotic disorders, such as the schizophrenias. Indeed, findings of a male propensity to poor premorbid adjustment, negative and non-affective symptoms, and poor outcome relative to their female counterparts, has led to suggestions that males are more prone to an early-onset dementia praecox type of schizophrenic disorder. The current study investigated a sample of 38 male and 20 female patients presenting with their first episode of psychosis (broadly defined, but excluding obvious drug-induced disorders) from a defined catchment area population, which had been systematically ascertained without prejudice to diagnostic subtype or illness duration. The study investigated gender, diagnosis and interaction of gender and diagnosis on differences within the three developmental age categories of childhood, early adolescence and late adolescence, to identify where, within these age categories, differences lie. The second part of the study was to investigate the relationship between premorbid adjustment, gender, and psychopathology as measured by the PANSS and SCL-90. General linear modelling revealed that males were reported to have had poorer premorbid adjustment in late adolescence when compared to females, notably in items examining school performance, adaptation to school, social interests and sociosexual development. Males were observed to have higher levels of negative symptoms but not for positive or general symptoms on the PANSS. This finding is independent from the effect of diagnosis or of the interaction effect between gender and diagnosis on premorbid adjustment. There were no gender effects for the self reported global indices on the SCL-90. The results suggest that in comparison with their female counterparts, males who develop a psychotic illness have significantly poorer premorbid adjustment at the late adolescent stage and that this may contribute to higher levels of negative symptoms.