CONTEXT Physicians have been encouraged to counsel families about risks associated with gun ownership, but the effectiveness of physician counseling regarding gun safety is unknown. OBJECTIVE To determine the effectiveness of gun safety counseling during well-child care visits. DESIGN Group randomized, controlled trial. Physicians, nurse practitioners, and physician assistants were randomized to either the intervention group or a control group. SETTING Group Health Cooperative, a staff-model health maintenance organization. Patients. Consecutive sample of families (n = 1295) seen for a scheduled appointment for well-child care for a child <18 years of age. Of the families originally scheduled for a visit, 80. 3% were seen and completed the outcomes surveys. INTERVENTION Each family in the intervention group was given a 60-second message by their practitioner that depended on the presence of guns in the home. Families without guns were informed of the health risks associated with gun ownership and given a standard information pamphlet. Families with guns were given the same information about risks and were told that if they chose to keep a gun, they should store it locked and unloaded. They were given instructions on storage and a folder with material, including the same pamphlet, a letter from the police department, written storage guidelines, and discount coupons for gun storage devices. MAIN OUTCOME MEASURE Changes in the following self-reported events: 1) acquisition of a safe storage device; 2) removal of firearms from the home; and 3) acquisition of firearms. Results. There were no important differences between intervention and control groups in the rate of acquisition of new guns (intervention: 1.3% vs control:.9%) after the intervention. Among households with guns at baseline, there were also no differences between groups in the removal of guns (intervention: 6.7% vs control: 5.7%), but there was a fairly large nonsignificant difference in the proportion who purchased trigger locks (intervention: 8.0% vs control: 2.5%). CONCLUSIONS A single firearm safety-counseling session during well-child care, combined with economic incentives to purchase safe storage devices, did not lead to changes in household gun ownership and did not lead to statistically significant overall changes in storage patterns.