ABSTRACT Purpose: We hypothesized that warm infusion solution should be used for urodynamic studies in children because it more closely simulates normal physiology. Thus, we conducted a prospective randomized study comparing consecutive room temperature (RT) and body temperature (BT) cystometrograms (CMG) in the same child. Materials and Methods: Subjects underwent identical CMGs using RT and BT saline in random order. Maximum cystometric bladder capacity (CBC), pressure at CBC, uninhibited detrusor contractions, detrusor leak point pressure, maximum flow rate, pressure at maximum flow, maximum voiding pressure, residual urine and pressure specific volumes below 20 and 30 cm water were compared. Data were analyzed using ANOVA, t test, and chi-square. Results: RT and BT CMGs in 44 males and 47 females with a mean age of 8.6 years were compared. Of the children 58 (64%) had spinal dysraphism, 8 (9%) had cerebral palsy, 5 (6%) had posterior urethral valves and 20 (21%) had recurrent urinary tract infection, daytime incontinence or frequency/urgency symptoms. Maximum CBC, pressure at CBC, and pressure specific volumes below 20 and 30 cm water were significantly lower (10% to 15%) during BT cystometry. Maximum flow rate was higher with BT saline. Detrusor leak point pressure, pressure at maximum flow, maximum voiding pressure, and residual urine did not differ. Uninhibited detrusor contractions were more frequent during RT infusions. No gender differences were found. The discrepancies between RT and BT cystometry were most prominent in infants, children with spinal dysraphism and children with large bladders. Conclusions: There is a difference between cystometries performed using RT and BT saline. Capacity, storage variables and detrusor activity are diminished during BT cystometry. Although statistically significant differences were found between consecutive RT and BT CMGs, the magnitude of the difference may not be clinically relevant to change management. As such, we do not believe it is necessary to use warm infusion solution on a systematic basis for urodynamic studies in children. However, for children younger than 2 years when the magnitude was more relevant, the use of warm solution is recommended.