The possibility of using bromocresole purple index (BCPI) for estimating trypsin inhibitor activity (TIA) in samples of soybeans processed by microwaves (with a radiation of 2 450 MHz working frequency) was tested. Ten intensity options of bean micronization were prepared and each of the three levels of radiant power (350, 500 and 650 W) had three processing times (60, 120 and 180 s) respectively, and one sample remained untreated. Seed micronization caused: the TIA decrease from 48.3 TUI/mg _d.m. (for raw sample) to 3.78 TUI/mg/g _D.M. (for heated - 180 s at 650 W power) and the BCPI increase from 22.63 mg/g_D.M (for raw sample) up to 50.05 mg/g_D.M (for heated -180 s at 650 W power). Due to the significant interdependence of the results obtained with the use of BCPI and TIA methods (coefficient of correlation r = - 0.99; fitting coefficient R²=97.63; trend line TIA = -1.65XBCPI + 89.98 to experimental data points), as well as to the high sensitivity (=0.30), detectability (=273.96 s), distinguishability ( = 97.22%) and low time-consumption ( = 1.5 h) the BCPI test was proved useful for a rapid estimation of trypsin inhibitor activity of micronized soybeans.