The effects of adding vanadium (up to 0.1%) and niobium (0.02%) to a steel containing 0.07%C - 1.5%Mn - 0.29%Si - 0.035%Al - 0.01%N have been studied in the laboratory. It was determined that a steel containing 0.05%V had a yield stress, after accelerated cooling, greater than 480 MPa and toughness, as measured by U-notch and Vee-notch impact specimens, improving as the finish rolling temperature was lowered from 950 degrees C to 750 degrees C. Consequently, a semi-industrial trial, involving the manufacture of a steel containing 0.07%V, rolled to 22 mm and 32 mm thick, narrow plates, was carried out. This demonstrated that after finish rolling at 750 degrees C, followed by air cooling, the steel had a yield strength in excess of 470 MPa accompanied by excellent toughness. The work demonstrates the potential for achievement of high levels of strength and toughness in heavy plate steels, micro-alloyed with vanadium.