Summary Introduction: Meeting the unmet need for family planning among reproductive age women of VCT clients improves health by fewer pregnancies, lower exposure to sexually transmitted infections and protection against ovarian cancer which indirectly reduces maternal morbidity and mortality. Objective: to assess demand for family planning service and associated factors among reproductive age women of VCT clients Hawassa town, south Ethiopia. Method: A cross-sectional study design with analytic component was conducted among 398 VCT clients drawn randomly from VCT site visitors in Hawassa town, SNNPRS from 25, Aug to 24, Sep 2010. Pre-tested and structured questionnaire was used to estimate the proportion of women VCT clients with the demand for family planning and associated factors. Data analysis was done using SPSS version 16 statistical package computer software. Association between dependent and independent variables was assessed by both bivariate and multiple logistic regression. Strength of association was presented using odds ratio and 95% confidence intervals Results: From the total of 406 women of VCT clients recruited, 398 responded to the questionnaire adequately making