CI-921, (9-[[2-methoxy-4-[(methylsulfonyl)amino]phenyl]amino]- N,5-dimethyl-4-acridinecarboxamide 2-hydroxyethanesulfonate (1:1)), an anilinoacridine derivative with activity in experimental solid tumors was studied in a multicenter phase II trial in patients with solid tumors. Eligible tumor types included cancers of the breast, stomach, pancreas, nonsmall cell lung, small cell lung, colon, head and neck area, and melanoma. Prestudy requirements included an ECOG performance status of < or = 2, no CNS metastases, and measurable disease. CI-921 was administered intravenously over 1-2 hours on days 1, 8, and 15 of a 35-day course at an initial dose of 270 mg/M2, with modification in subsequent courses based upon tolerance. Principal toxicities included leukopenia, marked phlebitis, and mild nausea and vomiting. One hundred fifty patients were entered of whom 132 were evaluable for response. There was one complete and one partial response among 19 patients with breast cancer, and two partial responses, one each among 14 head and neck and 36 nonsmall cell lung cancer patients.