The association of recent life stressor severity to putative biological markers of stress was examined in 34 newly admitted patients with acute psychosis. Of the biological variables examined, only pretreatment admission serum cortisol was correlated with stressor severity. Pretreatment serum prolactin, plasma homovanillic acid (HVA), and methoxyhydroxyphen-ethylglycol were not associated with severity of recent life stressors. We controlled for clinical and psychosocial variables that might affect the relationship of stressor severity to biological markers, and found that duration of psychotic symptoms was negatively correlated with stressor severity; however, when both cortisol and duration were entered in a stepwise multiple regression analysis, only pretreatment admission cortisol remained significantly and positively correlated with stressor severity. These findings suggest that serum cortisol may be a useful biological marker when investigating the relationship of life stress to episode onset. In addition, pretreatment HVA was correlated with early neuroleptic response but not with stressor severity, suggesting that HVA has value as a predictor of response independent of recent life stressors.