The primary aims were to study reasons for tooth extraction and explanatory factors of normative and perceived need for replacement. The study is based on nation-wide cross-sectional surveys in 1968, 1988 and 1998. A systematic random sample was drawn in 1998 to give 40% of dentists in Norway; collecting demographic and treatment data on 772 dentists, 1,164 patients, 1,495 teeth and 987 radiographs. In a time-trend perspective, all age groups experienced a decrease in extractions due to caries in 1968-88 while no change was found during 1988-98. The proportions of extractions due to periodontal diseases have remained stable during 30 yrs. Tooth type and number of teeth extracted were the most important predictors of the dentists recommending a replacement. Demographic characteristics had no effect on the dentists'' decision. 47% of the patients reported that a replacement was necessary while 16% were undecided. Patient and dentist agreed about the need for a replacement in 62%. Tooth type, service sector, number of teeth extracted and number of remaining teeth affected the likelihood of agreement about need for the replacement of teeth.