5-fluorouracil (5-FU) is still one of the most prescribed cytostatic drugs, but gastrointestinal toxicity limits its use. Capecitabine, an orally administered prodrug of 5-FU, is activated by a cascade of three enzymes, resulting in the preferential release of 5-FU at the tumor site; it was developed in an attempt to avoid the problem of gastrointestinal toxicity of fluoropyrimidines. The aim of the present study was to investigate the safety profile of capecitabine at the daily oral dose of 502 mg/m2, given in two divided doses 12 hr apart for at least 10 days of treatment. In conformity with Italian law, 11 patients (8 females and 3 males) with advanced or metastatic pretreated solid tumors (4 colon-rectum, 3 breast, 2 stomach, 1 ovary, 1 lung) were enrolled. Treatment duration ranged from 1.5 to 14 days. Ten of the 11 patients received the planned 10 days of treatment. One patient was discontinued on the second treatment day when he presented with symptoms of intracranial hypertension with multiple brain metastases documented by CT scan. Toxicity consisted of 1 case of mild edema; no adverse events characteristic of fluoropyrimidines were recorded. No abnormalities in hematologic, renal, hepatic or electrolyte values were seen. In conclusion, capecitabine, given at this dose and for a relatively short period, proved to be well tolerated. Further investigation is recommended to define the promising antitumor efficacy documented in many human xenograft models in mice.