Synopsis Destructive tests on prototype reinforced concrete slabs designed by Johansen's yield-line method and Hillerborg's strip method are described. All the slabs were square, simply supported and uniformly loaded. The yield and failure characteristics of these slabs are then compared with those obtained from slabs designed by an optimum lower-bound approach. The optimum slabs contained 37 % and 16 % less reinforcing steel than the slabs designed by Johansen's and Hillerborg's methods respectively.