An overnight slide-culture for the detection of group A streptococci was introduced in a Finnish health centre. The number of patients from whom a throat culture was obtained increased from 55% to 70% with the new method. Despite this increase, the prescribing habits of primary care physicians did not change. Treatment was in most cases (84-90% of those treated) still initiated before culture results were available, and antibacterial medication was discontinued only occasionally (1-3%). Physicians usually decided the treatment during the first consultation. These findings contradict earlier studies where prescriptions decreased during rapid culture. Use of throat cultures as diagnostic aid should be reconsidered, especially when more rapid methods now are available.