The quantity of bacteria of 500 urocultures was analyzed in the Laboratory of Clinical Pathology of the "Regina Elena" Institute of Rome (Italy). These evaluations were carried out both by the classic agar colony-count method (CC) and by a new colorimetric system (Dye test, Dt), recently introduced on the market. Using the CC system, 142 (28.6%) positive and 358 (71.8%) negative samples were found, considering the usual 100,000 CFU/ml to be the limit. The results of the colorimetric test were read on a graduated scale of red color. By means of a concordance analysis, a correct relationship between the color grade and the positivity of the samples was established. For this equivalence a more intense color than that suggested by the manufacturer was found. Furthermore an 89.7% rate of concordant and a 10.2% of discordant results were observed. These latter may be divided into two fractions: the first (4.6%) was Dt-positive and CC-negative (these samples are characterized by the presence of residual antibiotics in 78.3% of the cases); the second fraction (5.6%) was Dt-negative and CC-positive (characterized by a 67.9% of Pseudomonas sp. isolation frequency).