Some 4-anilinofuro[2,3-b]quinoline derivatives were synthesized from dictamnine, a natural alkaloid, and evaluated for their cytotoxicity in the NCI×s full panel of 60 human cancer cell lines derived from nine cancer cell types, including leukemia, non-small-cell lung cancer, colon cancer, CNS cancer, melanoma, ovarian cancer, renal cancer, prostate cancer, and breast cancer. 1-[4-(Furo[2,3-b]quinolin-4-ylamino)phenyl]ethanone (5) (mean GI 50 0.025 mm), bearing an 4-acetylanilino substituent at C(4) of furo[2,3-b]quinoline, was more active than its 3-acetylanilino counterpart 7 (mean GI 50 5.27 mm), and both clinically used anticancer drugs, N-[4-(acridin-9-ylamino)-3-methoxyphenyl]methanesulfonamide (m-AMSA; mean GI 50 0.44 mm) and daunomycin (mean GI 50 0.044 mm). Compound 5 was capable of inhibiting all types of cancer cells tested with a mean GI 50 of less than 0.04 mm in each case except for the non-small-cell lung cancer (average GI 50 1.75 mm). Although non-small-cell lung cancer is resistant to compound 5, the sensitivity within this type of cancer cells varies: HOP-62 (GI 50 < 0.01 mm), NCI-H460 (GI 50 0.01 mm), and NCI-H522 (GI 50 < 0.01 mm) are very sensitive, while HOP-92 (GI 50 12.4 mm) is resistant. Among these non-small-cell lung cancers, NCI-H522 was found to be very sensitive to 5, 8a, and 8b with a GI 50 values of < 0.01, 0.074, and < 0.01 mm, respectively.