Timely use of necessary follow-up services is an important dimension of ambulatory care quality. Using a hospital-based walk-in center, this study identified patients who were referred for follow-up care and examined factors related to compliance with these referrals. The participants were 696 adults seen in a hospital-based walk-in unit between June 1, 1992, and December 1, 1992. Patients completed a self-administered questionnaire including questions about sociodemographic characteristics, prior use of health services, and the Medical Outcomes Study (MOS) 36-Item Health Survey. Medical findings, follow-up recommendations, insurance status, and compliance with follow-up referrals were ascertained using chart review, the hospital's computing system, and clinic records. Fifty percent of the patients were referred for follow-up medical care; 55% of these complied with follow-up referrals. Factors associated with referral for follow-up care included older age, inability to afford a physician, longer duration of chief complaint, the patient's belief that follow-up care would be needed, and worse MOS pain score. The most important factor associated with compliance with follow-up referral was scheduling appointments while patients were still in the walk-in unit. Patients with such scheduled appointments were almost 10 times more likely than others to receive follow-up (adjusted odds ratio = 9.6, 95% confidence interval = 4.4-21.2). The most important step a provider can take to improve compliance with follow-up referral is to schedule appointments before patients are sent home. This should presumably improve quality of ambulatory care.