Objective To study the clinicopathologic features which influence the prognosis of patients with stage Ib nonsmall cell lung cancer (NSCLC) after operation, and discuss the indication of postoperative chemotherapy. Methods From January 2002 to December 2002, the clinical materials of 152 patients who underwent complete pulmonary lobectomy and were confirmed to have stage Ib NSCLC by postoperative histopathological examination were collected from Shanghai Chest Hospital. There were 82 male and 70 female cases aged from 33-80 years. The mean age was 63.0 years. KaplanMeier method was used to compare and analyze the age, gender, tumor diameter, tumor location, lymphatic or vascular carcinoma embolus, differentiation, pleural invasion and chemotherapy of patients. Cox regression model was used to do prognostic multivariate analysis to above factors. Results The 5year survival rate was 71.1%. The median survival time was 44.20 months. The results of single factor analysis showed that the tumor diameter was longer than 5 cm(χ2=4.020,P=0.042), lymphatic or vascular carcinoma embolus existed(χ2=14670,P=0.001), poorly differentiated tumor(χ2=8.395,P=0.004), and those whose tumors were located on middlelower lobars had a poor prognosis(χ2=3.980,P=0.045). The age(χ2=0.478,P=0.740), gender(χ2=0.571,P=0.450), pathological type(χ2=0.406,P=0.816), pleural invasion(χ2=0.022,P=0.882) and postoperative chemotherapy of patients (χ2=1.067,P=0.302)had no relationship with postoperative survival. The results of multivariate analysis showed that lymphatic or vascular carcinoma embolus(P=0.006,95%CI:1.491,10.524) and poorly differentiated tumor(P= 0.001,95%CI:0.116,0.578) were the main factors which influenced the survival rate of patients. Conclusion The tumor differentiation and lymphatic or vessel carcinoma embolus of patients with stage Ib NSCLC are important factors which influence prognosis and survival rate. The poorly differentiated tumor and lymphatic or vessel carcinoma embolus could be regarded as one of the indications of postoperative chemotherapy.