The polymorphonuclear neutrophil (PMN) appears to be an important cell in the protection of the host from pathogenic periodontal microorganisms and, despite some reports to the contrary, it is generally assumed that early-onset forms of periodontal disease (including both juvenile and rapidly progressing periodontitis) are associated with a defect in PMN chemotactic behaviour. The purpose of the present study was to examine the peripheral PMN chemotactic behaviour, using the under agarose method, in 4 groups, namely healthy periodontium group (n = 7), gingivitis group (n = 8), early-onset periodontitis group (n = 17) and adult periodontitis group (n = 8). PMN from early-onset periodontitis patients showed normal random and chemotactic locomotory behaviour when compared with those of PMN from subjects of the other groups. No statistically significant difference could be found among the 4 studied groups, with regard to spontaneous and oriented migration.