OBJECTIVE To investigate the prognosis of moderate chronic obstructive pulmonary disease (COPD) in the elderly patients, and to evaluate the factors for long term survival. METHODS From May 1993, a prospective cohort study was carried out, in which 191 elderly patients with moderate COPD were recruited in Shougang communities, Shijingshan District, Beijing. The general health state, arterial blood gas, pulmonary function test, electrocardiograph, chest X-ray and 6-minute-walk test (6MWT) were recorded. The patients were followed for 12 years. Univariate analysis of survival rate was performed by Kaplan-Meier method. The significance test was done by Log-rank method, and the baseline factors were analyzed using the COX regression model multiplicity. RESULTS During the 12 years of follow-up, 10 patients were lost because of migration. Twenty-six patients died of non-COPD diseases, while 52 died of COPD. The survival rate was 81.7% (156/191) in 5 years, and 56.9% (103/181) in 12 years. The result with COX multiplicity showed that the important factors for prognosis of the patients were body mass index [BMI, relative risk (RR) = 0.916, 95% confidence intervals (95% CI) = 0.841 - 0.996], forced expired volume in one second (FEV(1), RR = 0.999, 95% CI = 0.998 - 1.000), arterial partial pressure of oxygen (PaO(2), RR = 0.929, 95% CI = 0.892 - 0.967), 6MWT (RR = 0.997, 95% CI = 0.995 - 1.000) and P pulmonale of ECG (RR = 4.081, 95% CI = 1.567 - 10.624). CONCLUSIONS The important factors for prognosis of moderate COPD in elderly patients included BMI, FEV(1), PaO(2), 6MWT and P pulmonale in ECG.