This study aims to provide reference ranges of normal variability in urodynamic parameters through literature review of normal urodynamic values in the literature. Data were obtained through MEDLINE from articles published between January 1956 and February 2011, International Continence Society meeting abstracts and standardization reports. Search terms included urodynamics, bladder diary, uroflowmetry, frequency volume charts, pad tests, normal control, and normal volunteer. Normal values varied widely in the literature. However, with the help of clinical data, it was possible to define "normality" ranges for most of the different parameters. Urodynamic evaluation of lower urinary tract (LUT) function is not a physiological test. However, it is still the best available tool to assess LUT function. Even if normality in urodynamics can be defined, tests must always be interpreted against patient characteristics, complaints, and symptoms.