DUP is defined as the period between the onset of psychotic symptoms and the beginning of treatment. DUP is often prolonged and associated with poor prognosis. *Identify the DUP in a population of patients hospitalized, for a first episode of psychosis, in the psychiatric “A” service in Sfax Tunisia. * Investigate the clinical and social determinants of DUP. This is a retrospective study of 50 cases of patients, with a first episode of psychosis, admitted to the psychiatric “A” service during the month of August 2014. Sociodemographic and clinical characteristics were summarized using a comprehensive semi structured interview. Sociodemographic data: The average age of our patients was 37 years. 74% of participants were male. 62% of patients were single. 76% had a low socioeconomic level. The mean DUP was 72.13 weeks with a range of 0 weeks to 336 weeks. Data analysis shows that longer DUP was significantly correlated with: The insidious onset (p = 0.00), The late age at onset (p = 0.01), The predominance of negative symptoms (p = 0.04), The illiteracy (p = 0.008), The absence of family involvement in help-seeking (p = 0.01). There was no evidence of an association between DUP and any of the other variables considered: gender, living alone, socioeconomic level and subtypes of schizophrenia. The present findings suggest that DUP is influenced both by aspects of the clinical course and by the social context.