OBJECTIVE To investigate the clinical efficacy and toxic effect of the 3-dimensional conformal radiation therapy (3DCRT) for non-small cell lung cancer (NSCLC).METHODS Fifty-two patients with the Stage-I and W NSCLC were treated with 3DCRT. Cross analysis of the clinical data was conducted in the comparison between the 52 cases with 3DCRT and the other 50 cases with the conventional radiation therapy (CRT). In the 3DCRT group, only the primary tumor and positive lymph-node draining area were included in the clinical target area, setting 4 to 6 coplanar or non-coplanar irradiation fields, with 2 Gy or 3 Gy/fraction, 1 fraction a day and 5 fractions per week.The total dose ranged from a test dose (DT) of 66 Gy to 72 Gy. In the CRT group, the field area contained the primary tumor plus the homolateral hilum of the lung, the mediastinum superior or hol-mediastinum, and opposed anteroposterior irradiation. When the dosage reached DT 36～40 Gy, an oblique portal administered radiation was conducted in order to avoid injuring the spinal cord.The DT was 1.8～2.0 Gy/fraction, 1 fraction a day, 5 fractions per week, with a total dose of 60 Gy to 70 Gy.RESULTS The therapeutic effect (CR + PR) was 90.4% in the 3DCRT group, and was 72% in the CRT group. There was statistically significant difference between the two groups, P