In a previous paper a slight increase in gingival bleeding tendency was reported after the use of chlorhexidine rinses in dental students with clinically healthy gingivae. For further clarification of this finding the study was repeated using a split mouth approach. 30 dental students brushed the teeth in either the left or the right side of their mouth twice daily during a 7-day period. After each brushing, they rinsed for 1 min with 10 ml of a 0.2% chlorhexidine digluconate solution. Both the Plaque Index (P1I) scores and the bleeding tendency after massage of the gingival margin were low at the initial examination. The low P1I scores at baseline were further reduced on both sides of the jaws. On the side which was only rinsed the P1I scores were higher than on the side of combined mechanical and chemical cleaning. The gingival bleeding tendency was found to decrease on the brushed side and to increase on the side which was only rinsed. An increased bleeding tendency was most often observed in those individuals whose gingivae were the healthiest at baseline. A SEM analysis of the 2 sides of the dentition indicated that bleeding after chlorhexidine rinses may be associated with irritation from debris which, after the 7-day period of no mechanical oral hygiene measures, seemed to obliterate the gingival sulcus.