Usefulness of analytical method (bromocresole purple index – BCPI) as a new and fast way for available lysine (LA) content determination in micro-waved soybean seeds was tested. Due to a great interdependence of LA and BCPI determinations, which was confirmed by high correlation and determination coefficients values (r = 0.78 and R2) for proposed regression equations LA = f(BCPI), the BCPI method appeared to be useful for the description of available lysine (LA) content changes in micro-waved soybean seeds and soybean meal.