INTRODUCTION AND OBJECTIVES: We herein attempt to define which frequency-volume chart (FVC) parameters improve when nocturia improves.METHODS: A retrospective analysis of 24-hour FVCs was performed. Nocturnal urine volume (NUV, urine produced from time of retiring through first void upon arising), nocturia index (Ni, [NUV]/ maximum voided volume [MVV]), nocturnal polyuria index (NPi, [NUV]/ 24 hour volume), nocturnal bladder capacity index (NBCi, actual number of nocturnal voids [ANV]epredicted number of nightly voids [PNV, Ni-1]), and nightly urine production rate (NUP, [NUV]/hours of sleep) were all derived from FVCs. Improvement in nocturia was defined as !1 less episodes of nocturia in a single night. Two cohorts were constructed: one with patients who improved and one with patients who did not improve. A two-tailed T-test was performed to compare baseline differences between the two groups and to compare pre-vs. posttherapy FVC indices within each group.RESULTS: Forty-three men completed consecutive 24-hr FVCs (median age: 68, range: 50-91). Twenty-six men did not show improvement in nocturia (median age: 66, range: 50-87), whereas seventeen men did improve (median age: 69, range: 51-91). Those who improved had a median of 2 less nocturia episodes per night (range: 1-5). Baseline parameters of both cohorts revealed a difference (p<0.01) in Ni, with baseline Ni of 3.2 (AE1.24) in the improved group and 2.2 (AE0.64) in the non-improved group. Other baseline parameters were not significantly different. In the improved group, significant decreases were seen in NUV, Ni, NPi, NBCi, NUP and number of voids in 24 hours. Contrarily, in the non-improved group, significant increases were seen in NUV, Ni, NBCi, and NUP. Results are depicted in table 1. A chisquare test to compare treatment modalities showed no significant difference between groups (p¼0.567).CONCLUSIONS: Reductions in NUV, Ni, NPi, NBCi, NUP and number of voids in 24 hours were seen in patients with improved nocturia, yet increases in these parameters were seen in patients who did not respond to treatment. Improvement in nocturia was unlikely to be related to changes in overall bladder capacity, as there was no difference in MVV in either group. The results suggest that clinicians should target nocturnal diuresis rather than bladder capacity when treating nocturia.