A DISCUSSION on "Stress Analysis and the Designer" was opened by Sir Donald Bailey at the Birmingham Conference on April 13 of the Stress Analysis Group of the Institute of Physics. Sir Donald outlined his attitude to stress analysis as an engineering designer. He needed answers to particular problems which could not be obtained by mathematical methods either because of the complexity of the mathematical solutions or because of design assumptions, unknown boundary conditions or other practical uncertainties. He specified his requirements as the need to measure stresses up to 75–85 tons per sq. in. in steel or 25–30 tons per sq. in. in light alloys, occurring at frequencies from 0 to 25 cycles per second in structural work and up to 50 cycles per second in mechanical work. This required recording apparatus that would respond to at least 1,000 cycles per second. The stresses obtained should be correct to within 2½–5 per cent for all stresses from 4 tons per sq. in. upwards.