MTT assay, a sensitivity test of anti-tumor agents was performed, and its clinical usefulness, was discussed. In 15 surgical specimens, the cell suspensions were prepared aseptically, and divided into three processing; namely, Papanicolaou (Pap) smears to confirm the malignant cells, MTT assay, and cell cultures in chamber slides. MTT assay was evaluated only when tumor cells in the chamber slide were observed 50% or more by Pap staining. Drugs judged to be effective were applied for patients, resulting in 64.2% of predictive accuracy in the sensitivity. Conclusions; 1) MTT assay was developed for sensitivity test of anti-tumor agents, 2) Strict assessment was carried out by the confirmation of cancer cells using chamber slides, 3) On clinical usefulness, predictability for the sensitivity was 64.2%, that for resistance was 100%, and over all predictability was 66.7% 4) MTT assay was useful for the determination of effective and for elimination of ineffective drugs.