We tested the hypothesis that the expression of schizophrenic psychopathology is dependent on the stage of adolescent development. The study had a retrospective design, using high-quality case-note material of cases of schizophrenia at first admission. Patients with onset of illness between the age of 11 and 21 years were included. Sexual delusions were more apparent in females (OR = 3.6;95% CI 1.6-8.0), but otherwise no gender differences in the frequency of a range of positive symptoms were apparent. There was evidence that the age at which positive symptoms first appeared differed between males and females. The frequency of typical, 'first rank' schizophrenic symptoms such as auditory hallucinations, passivity phenomena and though interference, increased linearly with age in male patients, but did not vary with age in their female counterparts. The likelihood of displaying delusional beliefs such as persecutory delusions, explanatory delusions, delusions of reference and grandiose delusions increased with age in both sexes, but the association was stronger in males. The observation that typical schizophrenic symptoms in male patients are relatively uncommon during early adolescence, but increase as they grow older, could be explained by the later manifestation of puberty and associated maturational processes in boys.