Vaginal pH measurement is a screening method of vaginal infection in pregnancy. We tested two different methods of pH determination. In freshly taken vaginal fluid measurements were carried out with special pH indicator strips and pH micro glass electrode. About 100 microliters of vaginal fluid is enough when pH indicator strips are used, and 200 microliters when the micro electrode is used. The accuracy of the pH measurement by indicator strip is about 0.1-0.2 pH and by electrode 0.01 pH. Both methods show a good correlation between pH 4.0 to 7.0 (p = 0.0000). Until a pH of up to 4.3 we recommend the pH determination by indicator strips. In all cases with the possible risk of infection (pH values greater than 4.3) the micro electrode should be used.