After discussions on the need to measure the distribution of stress on the surface of a structure under load, and the connection between stress concentration, mechanical design and safety, a new technique for recording stress patterns called thermoelastic stress analysis (TSA) is described. For given material constants, the change in temperature on the surface of a structure, subject to dynamic loading, is directly proportional to the change in stress at that point. A specially designed, high-sensitivity I.R. camera is described which can present a colour display of the distribution of stress which could arise from temperature variations as small as 0·001 K resulting from a few units of microstrain in metals. A selection of typical results obtained by recording the stress concentration on the surface of a model pedestal structure are given to illustrate how TSA could be used as an aid to design. The likely useful areas of application of TSA can be identified with the help of a list of the principal characteristics of the method provided at the end of the paper.