The aim of the present study was to investigate the morphological features of supragingival plaque development in "rapid" and "slow" plaque formers using the replica technique. Forty-nine healthy volunteers were screened for their plaque formation rate after 3 days of oral hygiene abstinence using the plaque index (PI). Five subjects with the highest mean PI and six with the lowest mean PI were selected as "rapid" and "slow" plaque formers, respectively. After a series of thorough prophylaxis and oral hygiene instruction, all subjects went through a 14-day period of no oral hygiene to allow undisturbed plaque formation. Light body silicone elastomeric impressions were taken for the upper right central incisor of each subject on day-0, 1, 3, 7, and 14. Positive replicas were then poured from the impressions using epoxy resin and observed under a scanning electron microscope. A more complex supragingival plaque structure was seen in the day-1 and day-3 replicas of the "rapid" group compared to the "slow" group. From day-7 to day-14, during the maturation period of supragingival plaque, no discernible differences were noted between the two groups. Quantitatively, the percentage of plaque coverage on the tooth surfaces was higher in the "rapid" group than in the "slow" group in day-1 and day-3 replicas. These observations indicate that the morphological and topographical features of supragingival plaque in "slow" and "rapid" plaque formers differ, especially in the early developmental phase.