This paper examines the relationships between 3 clinical parameters: pocket depth, gingival index, and bleeding index and 2 laboratory parameters: spirochaete counts and motility counts on the basis of analysis of 883 observations made in the mouths of 41 patients. The results were consistent with the findings of other studies in that deeper pockets tended to harbour higher %s of spirochaetes and motile organisms. The same overlap between all the parameters in general and between spirochaetes and pocket depth in particular as existed in our previous study was demonstrably evident. 8% of shallow pockets had spirochaete counts in excess of 20% and 79% of deep pockets had spirochaete counts of less than 20, 18% having no demonstrable spirochaetes. These results are consistent with those of our previous study and with the findings of Evian et al. that even in pockets of the order of 7 mm, the proportions of spirochaetes found varies from what may be expected at healthy sites to what may be expected at diseased sites.