Recently marketed drugs have limited experience in clinical use. Follow-up evaluation is therefore needed, particularly when these drugs are "restricted use" medicines, such as the second-generation cephalosporins. We present a follow-up of the first use of cefonicid, which was carried out after its substitution for cefuroxime in our hospital. The indication for use, dosing, therapeutic effects, and possible adverse reactions were recorded in 210 of the first 319 medical-surgical inpatients who received cefonicid. Cefonicid was administered to patients who could have been treated with free-use antibiotics on at least 128 occasions; these were cases of community-acquired pneumonia without any risk factor, urinary tract infections, acute exacerbations in patients with chronic lung disease, surgical prophylaxis, and intraabdominal infections. One fatal case of Stevens-Johnson syndrome was seen. Other recorded adverse events were two skin reactions, one tachyarrhythmia with evidence of low cardiac output, six episodes of phlebitis, and nine superinfections during treatment with cefonicid. The use of cefonicid instead of cefuroxime was associated with 20 percent cost savings; however, this study shows that optimal antibiotic prescribing may produce much greater savings.