This pilot study aimed to identify early stages of chronic obstructive pulmonary disease (COPD) in an urban population of smokers and ex-smokers using the Global Initiative for Chronic Obstructive Lung Disease (GOLD 2001, 2003) classification guidelines and to assess the impact of early disease on quality of life. Smokers and ex-smokers of >or= 10 pack years and age >or= 50 years were recruited. After an initial telephone interview, eligible subjects completed a clinical assessment, spirometry tests, and the St. George's Respiratory Questionnaire (SGRQ). A total of 244 subjects completed the study; 91 subjects (37%) were normal, 153 subjects (63%) met the criteria for GOLD stages 0 to III: 65 stage 0 (27%), 43 stage I (18%), 38 stage II (16%), 7 stage III (3%) and 0 in stage IV. The stage 0 patients were younger than any other COPD groups (p<0.0005), including normal subjects (55.5+/-5.4 years vs. 59.6+/-7.2 years; p=0.0005). The frequency of current smoking in stage 0 patients was greater than those in the normal category (80% vs. 33%; p<0.0001). There were significant impairments in quality of life measures between normal subjects and all GOLD stages (SGRQ total scores; p<0.0001) except for stage I (SGRQ total scores; p=0.1409). Subjects with COPD at GOLD stage 0 were markedly under-diagnosed. These subjects had a significant impairment in their health-related quality of life measures, were younger than other categories, and were mostly current smokers. Thus, detection of COPD at GOLD stage 0 may provide a unique opportunity for early intervention and smoking cessation and the removal of GOLD stage 0 from the 2006 update should be re-assessed.