Doctors with longer consultation times tend to diagnose illnesses more precisely, prescribe fewer drugs and present better health advice to their patients. The aim of this study was to measure the average consultation time of general practitioners in Gorgan, Islamic Republic of Iran and to investigate the factors affecting consultation length, especially in relation to rational prescribing of drugs. Data were collected on 620 patient consultations with 62 randomly selected general practitioners. Mean consultation length was 6.9 (SD 2.6) minutes. Patient factors that were significantly associated with a longer mean duration of consultation time were higher number of health problems, older age and fewer items of previously used drugs. Physician factors that were significantly associated with a longer mean consultation time were younger age, higher numbers of items prescribed and injectable drugs prescribed, frequency of interruptions and higher workload.