Objective: To determine the diagnostic accuracy of urinalysis and Gram staining the diagnosis of urinary tract infection (UTI) in pregnancy. Materials and methods: Diagnostic validity study in pregnant women with a high suspicion of UTI, hospitalized in the Obstetrics and Gynecology Service of the Simon Bolivar Hospital, a Level III center, between January 1st 2009 and December 31st 2010. Gram staining and urinalysis with its parameters (leukocyte esterase, bacteriuria, leukocyturia, nitrites) were compared with urine culture, considered as the gold standard test. Specificity, sensitivity, positive predictive value (PPV) and probability ratios (LR + and PR -) were calculated. A non-probabilistic sampling was done out of convenience. The sample size was calculated using the Epidat 4.0, with a minimum expected sensitivity of 90% and a confidence level of 90% for the prevalence of 20% established in the literature. Results: Of the total of 212 samples of pregnant women included in the study, 115 (54%) had a positive urine culture and 97 (46%) had a negative culture. Seventy-eight per cent of patients presented with pyelonephritis, while 22% presented with low UTI (cystourethritis). The most frequent germ was Escherichia coli, found in 70% of patients. Gram stain had a sensitivity of 74% (95% CI: 65-81) and a specificity of 86% (95% CI: 78-92); urinalysis had a sensitivity of 21% (95% CI: 14-29) and a specificity of 92% (95% CI: 84-96). Conclusion: Rapid tests done in the emergency room showed high specificity for the diagnosis of UTI in pregnant women. Gram staining is the test with the highest sensitivity for the diagnosis of UTI in this population at Hospital Simon Bolivar.