Spatial autocorrelation analysis attempts to measure the extent to which variation in spatially distributed data is due to the existence of contiguity relationships. From a mathematical point of view there are two general approaches to the problem : analysis of variance, and the calculation of a coefficient of spatial autocorrelation. In this study a method of the second type is applied, first to a series of test patterns with varying degrees of spatial autocorrelation, and then to the spatial distribution of chronic disease mortality in Montréal in 1972. The conclusion of the mortality data analysis were that a slight but significant autocorrelation effect was present and that other factors indicated in the recent medical geography literature could well be more influental than spatial contiguity itself.