A study of lichen succession on seven rock surfaces of recent origin occurring below timberline in the North Canterbury high country, New Zealand, is described. Trends derived from data on occurrence of species, number of species, and total lichen cover were found to have a general correlation with age. Some of the variation in the values obtained could be attributed to the effect of stone size. The computing of negative exponential curves for three 40 yr old surfaces indicated that clear asymptotic levels could be defined for the relationship between numbers of species per stone and stone area. These asymptotes provide a means of eliminating variability attributable to stone size from the data, enhancing the possibility of using the general trends described as a means for dating rock surfaces. Further variation in the data appeared to be the result of environmental differences.