As decided in the protocol, the AICLA study ended when all the 604 patients had completed a follow up of three years. Adhesion to the protocol and drug compliance were excellent. Side effects, particularly peptic ulcers and bleedings of various origins were more frequent in the 2 treatment groups containing aspirin. The number of fatal and non fatal cerebral infarction was 31 in the P group, 17 in the ASA group, and 18 in the ASA + D group. Taking into account the duration of follow up for each patient, these figures correspond to cummulate rates of 18 p. 100 in the P group and 10.5 p. 100 in the 2 others. Analysis with the Mantel Method showed: 1 - a difference at the 6 p. 100 level between the 3 groups and between P an AD; 2 - A difference at the 5 p. 100 level between P and A; 3 - No difference between A and AD; 4 - A difference at the 2 p. 100 level between the P group and the two treated groups taken together. Among other diseases occurring during the trial, the only significant difference concerned myocardial infarction, less frequent in the 2 treated groups (p less than 0.05). Subgroup analysis failed to show a significant sex difference in the efficacy of aspirin. It is concluded that, in patients such as those defined in the protocol, Aspirin (1 g) has a significant beneficial effect in the secondary prevention of atherothrombotic cerebral infarction.