The aim was to investigate the morphological features of supragingival plaque development in 'rapid' and 'slow' plaque formers using scanning electron microscopy (SEM). Forty-nine healthy volunteers were screened for their plaque-formation rate after 3 days of oral hygiene abstinence using the Plaque Index (PI). Five with the highest and six with the lowest mean PI were selected as 'rapid' and 'slow' plaque formers, respectively. Six enamel blocks measuring 2 x 2 x 1 mm were bonded onto the buccal surfaces of the upper left canine, premolars and first molar of each selected participant after a series of prophylaxes and oral hygiene instruction to ensure clinical gingival health. A 14-day period with no oral hygiene began thereafter. An enamel block was removed at 3 hr, 6 hr, 1 day, 3 days, 7 days and 14 days from each individual, fixed, and processed for SEM. Quantitatively, more bacteria were observed on the 3-hr to 1-day enamel blocks of the 'rapid' plaque formers. The day-1 specimens of the 'rapid' group showed a more complex supragingival plaque structure than those of the 'slow' group. From days 3 to 14, during the maturation period of supragingival plaque, there were no discernible differences between the two groups except that intermicrobial matrix was more prominent in the 'rapid' group. In general, the development of supragingival plaque followed known patterns. These observations indicate that morphological features of supragingival plaque in 'slow' and 'rapid' plaque formers differ, especially in the early developmental phases.