Quality control surveys combined with teaching courses and expert consultations were offered to laboratories serving general practitioners in the county of Sør-Trøndelag, Norway. Fifty-one laboratories participated in the programme and the surveys during 1988-89. During the study period the number of laboratories having acceptable accuracy of their haemoglobin determination increased from approximately 80% to more than 90%. A similar increase was found also in precision where CV declined from 6.7% to approximately 2%. Additional positive effects were more close co-operation and more fruitful dialogues between the specialist laboratory and that of the general practitioners. The results offer promising perspectives to the control of laboratory performance in primary health care and the optimal use of laboratory tests.