Objectives. This study evaluated the effectiveness of a low-intensity dietary intervention in primary care practice in lowering dietary fat intake and raising dietary fiber intake. Methods. A randomized controlled trial of 28 physician practices in six primary care clinics enrolled, by telephone, adult patients who had appointments for nonurgent nonacute visits. Of 3490 eligible patients contacted, 2111 completed baseline interview; 86.1% also completed a 12-month follow-up. Physicians gave intervention participants a self-help booklet and a brief motivational message. Changes in fat and fiber from baseline to 12-month follow-up were evaluated. Results. Intervention and control groups both reported a decrease in fat intake and an increase in fiber intake. The differential change and 95% confidence interval (CI) for the percentage of energy obtained from fat was -1.2 (CI = -0.71, -1.7) (P = .0015), for grams fiber/1000 kcal 0.32 (CI = -0.066, -0.71) (P = .086), for fat score -0.044 (CI = -0.016, -0.072) (P = .010), and for fiber score 0.036 (CI = 0.011, 0.061) (P = .014), with greater reductions in fat and greater increases in fiber in the intervention group. Conclusions. This low- intensity intervention was effective in dietary behavior change.