A phase II trial was designed to evaluate the efficacy and toxicity of gemcitabine in patients with non-small-cell lung cancer (NSCLC) previously treated with platinum-containing regimens and prospectively categorized for platinum response status. Treatment consisted of gemcitabine 1000 mg/m2 given intravenously on days 1 and 8 of a 21-day cycle. The status of p53 in pretreatment tumor tissue was assessed by immunohistochemistry (IHC). Sixty-one patients who progressed or recurred following platinum-based therapy were enrolled, 26 platinum-sensitive and 35 platinum-refractory. A median of 4 treatment courses (range, 2-7 courses) was delivered. Of the 55 patients assessable for response, there was 1 confirmed complete response and 3 with a confirmed partial response for an overall response proportion of 7%. Twenty-one patients had stable disease while 28 progressed and 2 patients had an unconfirmed partial response. Three of the responders (2 confirmed, 1 unconfirmed) were platinum-refractory. Median progression-free survival (PFS) and overall survival for all patients were 4.1 months and 8.6 months, respectively. Median PFS and overall survival for the platinum-sensitive and platinum-refractory cohorts were 5.4 months versus 3.1 months, and 11.9 months versus 7.1 months, respectively. Toxicity was principally hematologic with grade 3/4 neutropenia in 21% and grade 4 platelets in 8%. There were no treatment-related deaths. Twenty-four of 33 patients (73%) had p53-positive tumors. Although no significant association between platinum sensitivity and p53 status was seen, patients with platinum-sensitive disease and negative p53 by IHC had a trend toward longer survival compared to those with platinum-refractory disease and/or p53 positivity (P = 0.06). We concluded that salvage gemcitabine in this dose and schedule is safe and tolerable in previously platinum-treated patients with NSCLC.