In recent years the technology of low-alloy TRIP steels has considerably advanced. The mechanical properties are characterised by a combination of high yield strength and high uniform elongation as well as enhanced formability. In the present work an ellort to correlate mochallical properties with the retained austenite stability was made. Two low-alloy TRIP steels were investigated. The first of them represents a typical composition of the low-alloy TRIP steels, while the other one contains aluminum as aUoying etement. The influence of the heat treatment on the mechanical properties and especially on the amount and stability of the retained austenite was determined. The retained austenite stability was measured with a sing!e specimen technique. in which a tensile specimen was used to determine the M~ temperature with a loading-unloading procedure. The results showed that there is a slrong influence of the stability of the retained austenite on the mechanical properties. Increased stability combined with a high amount of retained austenite, exhibited an increase in both, yield strength and uniform elongation while increased amount of retained austenite with low stability did not show the same good combination of mechanical properties. The results clearty indicate that in order to get the maximum TRIP effect. a good combination of austenite stabHily and amount is required.