STUDY OBJECTIVE: To study the clinical and cost outcomes of providing nutritional counselling to patients with one or more of the following conditions: overweight, hypertension and type 2 diabetes. DESIGN: The study was designed as a random controlled trial. Consecutive patients were screened opportunistically for one or more of the above conditions and randomly allocated to one of two intervention groups (doctor/dietitian or dietitian) or a control group. Both intervention groups received six counselling sessions over 12 months from a dietitian. However, in the doctor/dietitian group it was the doctor and not the dietitian who invited the patient to join the study and the same doctor also reviewed progress at two of the six counselling sessions. SETTING: The study was conducted in a university group general practice set in a lower socioeconomic outer suburb of Perth, Western Australia. PATIENTS: Of the 273 patients randomly allocated to a study group, 198 were women. Age ranged from 25 to 65 years. Seventy eight per cent of patients resided in the lower two socioecnomic quartiles, 56 per cent described their occupation as home duties and 78 per cent were partnered. RESULTS: Both intervention groups reduced weight and blood pressure compared with the control group. Patients in the doctor/dietitian group were more likely to complete the 12 month programme than those in the dietitian group. Patients in the doctor/dietitian group lost an average of 6.7 kg at a cost of $A9.76 per kilogram, while the dietitian group lost 5.6 kg at a cost of $A7.30 per kilogram. CONCLUSION: General practitioners, in conjunction with a dietitian, can produce significant weight and blood pressure improvement by health promotion methods.