Purpose: To investigate the relationship between expression of cell cycle-related protein cyclin D1, p27kip1 and the pathogenesis of bronchioloalveolar carcinoma (BAC) and the value of prediction of prognosis. Methods: Cyclin D1 and p27kip1 protein were detected by immunohistochemical En Vision method in 43 BACs. Results: The positivity of cyclin D1 in BAC was 65.1% (28/43), which was significantly higher than that in normal pulmonary tissue (0/13), P<0.01. No statis-tically significant association was found between cyclin D1 expression data and sex, age, tobacco-use history, histologic subtype (mucinous vs nonmucinous), stromal fibrosis, lymph node metastasis, clinical stage or postoperative survival period (P>0.05), while cyclin D1 expression was found to be negatively correlated with tumor size (P<0.05). The positivity of p27kip1 in BACs was 51.2% (22/43), significantly lower than that in normal pulmonary tissue (12/13), P<0.01. p27kip1 expression level was not associated with sex, age, tobacco-use history, tumor size or histologic subtype (P>0.05), but was negatively correlated with stromal fibrosis, lymph node metastasis and clinical stage (P<0.05); and positively associated with postoperative survival period (P<0.01). The survival rate of p27kip1 positive group was significantly higher than that of p27kip1 negative group (P<0.01). No statistically significant correlation was found between cyclin D1 and p27kip1 expres-sion. Conclusions: Increased cyclin D1 expression and decreased p27kip1 expression are related to the pathogenesis of BAC; decreased p27kip1 expression is associated with metastasis progression; immunodetection of p27kip1 is useful for assessment of prognosis. Methods: To investigate the relationship between expression of cell cycle-related protein cyclin D1, p27kip1 and the pathogenesis of bronchioloalveolar carcinoma (BAC) and the value of prediction of prognosis. Methods: Cyclin D1 and p27kip1 proteins were detected by immunohistochemical Envision method in 43 BACs. Results: The positivity of cyclin D1 in BAC was 65.1% (28/43), which was significantly higher than that in normal pulmonary tissue (0/13), P <0.01. No statis-tically significant association was found between cyclin D1 expression data and sex, age, tobacco-use history, histologic subtype (mucinous vs nonmucinous), stromal fibrosis, lymph node metastasis, clinical stage or postoperative survival period (P> 0.05) The positivity of p27kip1 in BACs was 51.2% (22/43), significantly lower than that in normal pulmonary tissue (12/13), P <0.01. p27kip1 expression level was not associated with sex, age, tobacco-use history, tumor size or histologic subtype (P> 0.05), but was negatively correlated with stromal fibrosis, lymph node metastasis and clinical stage (P <0.05) . The survival rate of p27kip1 positive group was significantly higher than that of p27kip1 negative group (P <0.01). No significant correlation was found between cyclin D1 and p27kip1 expres-sion. Conclusions: Increased cyclin D1 expression and decreased p27kip1 expression are related to the pathogenesis of BAC; decreased p27kip1 expression is associated with metastasis progression; immunodetection of p27kip1 is useful for assessment of prognosis.