Purpose: The objective of this study was to assess the practicability and effectiveness of group oral hygiene instruction for adults in comparison with individual oral hygiene instruction. Materials and Methods: A total of 104 male subjects aged 18 to 54 (mean age: 29.7) years were randomly assigned to one of four groups: group A was given individual oral hygiene instruction; group B was given group oral hygiene instruction; group C was given a combination of individual and group oral hygiene instructions; and group D received no oral hygiene instruction (the control group). The success of each form of instruction was evaluated on the basis of four parameters: (1) the Quigley-Hein plaque index (QHI), (2) the approximal plaque index (API), (3) a modified sulcus bleeding index (SBI) and (4) the community periodontal index of treatment needs (CPITN). All participants had professional tooth cleaning at the end of the baseline examination. The final examinations were conducted 13 weeks later. Results: All subjects showed a poor oral health status at the beginning of the study, and the mean QHI score was 2.2. In addition, 92% of all subjects had an API score of more than 70%. Moderate-to-severe gingival inflammation (modified SBI) was observed in 67.3% of the subjects. CPITN scores of 2 or 3 were calculated for 82% of all sextants. At the end of the study, all groups showed a significant improvement in their oral health status and periodontal parameters (P 0.0001). The majority of the subjects achieved an API score between 25% and 70%, and they had a mean QHI score of 1.2. A CPITN score of 0 or 1 was recorded for most sextants (62%). There was no significant difference between the various groups. Conclusions: This study demonstrated that group oral hygiene instruction and conventional individual instruction have similar beneficial effects in adults. Keywords: adults, group prophylaxis, individual prophylaxis, oral hygiene instruction