The consistency of penicillin allergy documentation in the patient chart, pharmacy profile, and medication administration record was assessed, along with the correctness of the self-reported patient history of penicillin allergy. One hundred fifty adult inpatients with a reported penicillin allergy were interviewed about their allergy. Questions included length of time since the allergic reaction, symptoms of the reaction, and whether rechallenge was ever attempted. Patients were classified into categories of (1) more severe allergy, (2) less severe allergy, or (3) intolerance on the basis of results of the interview. The patient pharmacy profile, chart, and medication administration record were reviewed to determine whether the allergy label was present. Patients who received antimicrobials during their hospitalization were evaluated. Of 117 patients, 82.9% were classified as allergic and 17.1% as intolerant. The allergy was documented in 98.7% of patient charts and 96.7% of medication administration records. The symptoms of the allergic reaction were described in the chart for only 34% of patients. Agents substituted for penicillin were potentially more toxic in 70.4% of cases, equally effective in all cases, and more costly in 55.5% of cases. Most, but not all, patients labeled as penicillin allergic had a history consistent with an allergy to the drug. Pharmacists can help ensure accurate allergy documentation by evaluating patients and educating both patients and health care professionals.