There is growing evidence for a relationship between the duration of untreated psychosis (DUP) and the prognosis in schizophrenia. The objective of this study is to evaluate whether DUP and premorbid level of social functioning are related to treatment response in acute treatment of first-episode schizophrenia. Seventy-nine first-episode schizophrenia patients were assessed with BPRS, SAPS, and SANS on admission and discharge during their first hospitalisation. Percentage of the difference between admission and discharge in total scores of all scales were taken as measures of absolute symptom reduction. The median DUP was 6 months (mean=8.6). DUP was correlated with reduction in BPRS and SAPS scores but not SANS scores. Patients with a short DUP (n=41) also showed a higher reduction in BPRS, and SAPS scores than those with a long DUP. Premorbid Adjustment Scale (PAS) scores were inversely correlated with age at onset and positively correlated with BPRS scores at admission. We did not find any relationship between PAS scores and response to treatment. Our findings suggest that DUP may be an important predictor of response in acute treatment of first-episode schizophrenia and thus, attempts for early diagnosis may also have a positive effect on acute treatment response.