ABSTRACTThe Periodontal Treatment Need System (PTNS) was applied to a population group to test the system in the field. Three hundred and seventeen employees in a factor; in Oslo, Norway, were examined. Their need for periodontal treatment was estimated. Examples of manpower and cost calculations were formulated. The needs were also studied according to age, sex and income distribution. Age was found to be the important variable. Six stratified subsamples, based on age and sex distribution, were drawn. Ten, 20 and 30% subsamples resulted in fairly accurate calculations when compared with the actual PTNS values. The application of the PTNS in the field indicated that the need for both preventive and interceptive periodontal therapy can be evaluated. From the PTNS scores, planning of manpower and thereby estimations of the costs to provide treatment were obtained. The system seemed to be simple and quick to apply.