To investigate the differential diagnostic capacity of the frequency-volume chart in 132 women with urinary incontinence. For each patient, the readings of two 24-h frequency-volume charts were compared to the urodynamic diagnosis which was used as the gold standard in 73 genuine stress incontinent women, in 23 urge incontinent women, and in 36 women with mixed incontinence. The total voided volume, the mean voided volume, the largest single voided volume, and the smallest single voided volume were statistically differentiating single parameters among the three groups (p<0.05). Applying logistic regression to the two well-defined groups of patients, the one with urge incontinence and the one with genuine stress incontinence, the frequency of micturition during nighttime revealed the best discriminatory power for these conditions. This study shows that in the frequency-volume chart micturition during nighttime discriminates best between urge and stress incontinence.