INTRODUCTION: There is a controversy about the effect of increasing venous hydration on the duration of normal delivery. With respect to the importance of this subject, various studies have been performed. The aim of the present study was determing the effect of overhydration on the duration of normal delivery. MATERIALS & METHODS: The statistical popultion included 52 women who referred to obstetric department of Sanandaj Besat hospital for normal delivery. These women divided randomly into control and treated groups. The type of study was double blind randomized clinical trial. After the beginning of active phase of labour, 250cc/h ringer lactate in treated group and 125cc/h in control group was administered intravenously by an experiencd midwife and labour process was evaluated. Data was analysed using k2 and t-tests.RESULTS: The results of this study showed no significant difference between the means of active phase time, stage II and III of labour in two groups. The mean of labour time was 232.1 ± 94.8min in treated group and 240.2 ± 108 min in control group.CONCLUSION: According to the results of this study venous hydration does not affect normal delivery time. Extensive studies with more samples are recommended.