The response of the common wheat line 'Chinese Spring' to heat shocks of different time lengths was studied by the two-dimensional (2D) electrophoresis of denatured proteins. After a heat shock of 5 h, 33 heat shock proteins (HSPs) accumulated in an amount sufficient to be revealed by silver stain. Two other wheat lines ('Moisson' and 'Selkirk') were then submitted to a heat shock of 5 h, and the responses of the 3 lines were compared: of a total of 35 HSPs, 13 (37.1%) were quantitatively or qualitatively variable. This variability concerns low-molecular-weight and high-molecular-weight HSPs. The three genotypes showed thermal tolerance but 'Chinese Spring's' response to heat treatments was slightly different from those of the other two lines The possibility of a relationship between HSP patterns and thermal sensitivity is discussed.