Gemcitabine is a novel nucleoside analog with demonstrated efficacy across a range of solid tumors. This paper reviews the single-agent safety profiles of 979 patients in 22 completed clinical studies using a day 1, 8, 15 q 28 day, 800-1250 mg/m2 dose schedule. Hematological toxicity was mild with WHO grade 3 and 4 toxicities recorded for hemoglobin (6.8 and 1.3% of patients), leukocytes (8.6 and 0.7%), neutrophils (19.3 and 6.0%) and platelets (4.1 and 1.1%). Myelosuppression was short lived and rarely of clinical significance. Mucositis and alopecia were rare, and nausea and vomiting mild. Transient rises in transaminases, mild proteinuria and hematuria were common, but rarely clinically significant. Renal failure of uncertain etiology was reported in seven instances. Some patients (18.9%) experienced transient flu-like symptoms and mild fever was reported in 37.3% of flu patients. Peripheral edema was reported in 20.3% of patients in the absence of cardiac, hepatic or renal failure. Thus, gemcitabine is well tolerated and has a mild toxicity profile. Of nearly 11,000 protocol-defined injections, 94% were administered and only 14% were reduced. Grade 3 or 4 non-laboratory toxicities with a frequency of more than 1% were only seen for infection (1.2%), nausea and vomiting (18.4%), and pulmonary toxicity (1.4%).