Between October 1985 and March 1987, 92 patients were registered on a phase II study of the Northern California Oncology Group investigating the importance of dose intensity in the treatment of advanced non-small cell lung cancer (NSCLC). Treatment consisted of high-dose cisplatin in hypertonic saline (200 mg/m2 on a 28-day cycle) given in a divided day 1 and day 8 schedule. The response rate among 76 assessable patients was 36% (27/76), with complete response (CR) in 8% (6/76) and partial response (PR) in 28% (21/76). If all patients receiving any drug therapy were considered, the overall response rate was 31% (27/87), with CR in 7% (6/87) and PR in 24% (21/87). Median survival times for all assessable patients and all patients receiving any therapy were 37 and 35 weeks, respectively. With the use of a protocol design specifying dose delays rather than dose reduction for toxicity, the mean dose intensity delivered was 47.2 mg/m2 per week, or 94% of projected. Compared with other dose-intensive regimens of cisplatin, this day 1 and day 8 schedule was relatively well tolerated, with peripheral neuropathy as the dose-limiting toxicity. The data on response and median survival times among patients receiving this single-agent therapy are encouraging. They support the potential importance of cisplatin dose intensity in the treatment of NSCLC. Whether these results represent a positive dose-response effect in NSCLC will be tested in a randomized comparative trial of high-dose versus standard-dose cisplatin therapy.