We compared the effectiveness of different methods of rapid diagnosis in the detection of asymptomatic bacteriuria in 74 females during the first trimester of pregnancy. The sensitivity, specificity and negative predictive value for the visual reading of nitrites, leukocyte sterase, bacteriuria and leukocyturia in the sediment and bacteria in Gram stain were 77%, 22%, 33%, 22% and 88%, 98%, 85%, 82%, 91% and 86%, and 97%, 89%, 90% and 90%, with and accuracy of 96%, 77%, 76%, 82% and 86%, respectively. The combination of visual readings of nitrites and Gram stain showed a sensitivity and negative predictive value of 100%. We conclude that if the reading of the reactive strip is negative, the likelihood of a positive culture is very small, and it is minimal when combined with Gram stain.