The urinary tract infections (UTIs) are one of the most common community and hospital acquired infections. The rapid diagnosis and the adequate etiological therapy are factors with direct impact on the morbidity and mortality associated with these infections. The aim of this study was to evaluate the HB&L Uroquattro instrument (ALIFAX, Italy) and the Residual Antimicrobial Activity test (RAA) for rapid and correct diagnosis of UTIs in ambulatory patients in Varna city, Bulgaria during a seven-month period (October 2020 - April 2021). Material and methods: A total of 1620 urine samples, collected prospectively from 842 ambulatory patients with symptoms of UTIs were studied. All patients report an information about recent antimicrobial treatment. All samples were screened for bacterial growth using 4 – hour protocol and were tested for RAA by HB&L Uroquattro. Simultaneously the samples were inoculated on Blood agar, CLED, CPS, Mc Conkey agar plates. Results: A total of 343 urine samples (21.2%) were positive for bacterial growth by the rapid screening method. The standard cultural method was positive in 22 % (n=352). RAA was detected in 5.6 % (n=91). A total of 113 patients (13.4%) gave information for therapy with antimicrobial agents or substances with potential antimicrobial activity. Among the samples that demonstrated positive RAA, 69.2 % (n=63) were positive for bacterial growth and 30.7 % (n=28) were negative. RAA results were negative in 19 patients who informed about recent therapy with antimicrobial agents, while in the rest 94 patients the RAA test was positive for bacterial growth from the screening. Conclusion: A very good correlation between the results from the automated HB&L Uroquattro instrument and those from the traditional cultural method was found. The RAA positive results were detected in patients, receiving antimicrobial treatment. The RAA test result is of great value for correct interpretation of the culture test and help to avoid the reporting of false negative results.