Detailed stress distributions along the axes of symmetry of a series of doubly convex cylindrical discs subjected to diametral loading have been obtained using the 'frozen-stress' and 'scattered-light' photoelastic techniques. The dependence of these stresses on (i) face curvature and (ii) cylinder thickness has been established. The results are discussed in relation to the stress distributions and brittle fracture characteristics of the plane-faced disc (i.e. the 'Brazilian' disc specimen) in the same loading mode.