It was hypothesized that subjects with chronic obstructive pulmonary disease (COPD) receiving long-term oxygen via nasal cannulas have an impaired sense of smell and/or taste. To objectively evaluate the sense of smell and taste, this study used the University of Pennsylvania Identification Test (UPSIT), a 40-item "scratch-n-sniff" test and a 20-item taste test using the four basic taste sensations of sweet, salt, sour, and bitter. Twenty subjects (15 male, 5 female) with severe COPD receiving long-term oxygen therapy (group 1), and an equal number of age- and sex-matched subjects with COPD not receiving oxygen therapy (group 2), and a healthy control group (group 3) were studied. Twelve subjects (seven male, five female) from group 1 subsequently underwent transtracheal oxygen catheter installation. Mean +/- SD for the basic smell test was significantly greater in group 3 (35.35 +/- 3.58) as compared with group 1 (27.70 +/- 6.07) or group 2 (31.10 +/- 4.95) (p less than 0.005). The difference between group 1 and 2 was not significant (p = 0.066). However, when adjusted for pack years of smoking, there were no significant differences between the three groups. Mean +/- SD correct responses for the basic taste test were significantly greater in group 3 (15.75 +/- 1.81) as compared with group 2 (12.8 +/- 2.78) (p less than 0.005) and group 1 (14.00 +/- 2.33) (p less than 0.05). There was no significant difference between group 1 and 2. The corrected data for taste, adjusted for years since quitting smoking, did not alter the basic differences between the groups. Mean smell and taste test scores were essentially unchanged in 12 subjects after six months of transtracheal oxygen therapy. Long-term oxygen use via nasal cannulas in this group of subjects with COPD did not appear to impair their sense of smell and taste. Smoking had a significant but variable effect on the sense of smell and taste.