The role of chemotherapy in the treatment of non-small cell lung cancer (NSCLC) has increased greatly in the past few years. While cytotoxic drugs are currently used both as single agents and in combination for palliation in locally advanced and metastatic disease, they have also been incorporated into multi-modality treatment strategies of Stage I to Stage III NSCLC. One of the main reasons for the increased acceptance of chemotherapy is the development of new substances. Among the most promising of these new drugs is the antimetabolite gemcitabine. Several single-arm gemcitabine Phase II studies involving more than 400 patients show validated response rates in more than 20% of the patients. These positive results have also been confirmed in randomized Phase II studies. Gemcitabine's unique mechanism of action, its lack of overlapping toxicity with other agents, and its favorable toxicity profile also define it as an ideal candidate for combination therapy. The activity seen with single-agent gemcitabine therapy can be compared with that of cisplatin-etoposide combination therapy. Gemcitabine-cisplatin combination response rates range from 31% to 54%, with a median survival time between 8.4 and 15.4 months and a 1-year survival rate between 30% and 59%. In addition to the clinical research of gemcitabine-cisplatin combinations, gemcitabine has also been tested in various double and triple combinations with carboplatin, paclitaxel, docetaxel, vinorelbine, and ifosfamide. Investigations combining gemcitabine with radiation therapy are on-going. The following review will summarize results from representative Phase I/II and III studies using gemcitabine for NSCLC patients.