The objectives of this study were to describe the operating conditions of dry chemistry instruments in primary care, as well as to elucidate financial aspects in general practice fee-for-service settings. We used questionnaires mailed to all users of the two most used dry chemistry instruments in Norway, as well as to a 14% random sample of Norwegian GPs. The overall response rate was 79%. The mean number of dry chemistry analyses varied considerably between individual users, but in general a substantial number of analyses were carried out. Even though most analyses on the instruments' repertoire were available in all user groups, a total of 13 additional constituents were suggested to be included in the repertoire. In occupational health care most results were ready when the client was present; this was not the case in general practice. The instruments were more profitable when more constituents were analysed per sample, although profitability varied substantially in the period studied (1986–1989). A discrete time history event analysis revealed that net profit earned, lower instrument price, available information about the technology and being in solo practice significantly influenced the decision to buy an instrument in fee-for- service practices.