Twenty-two subjects with documented COPD and no other significant illnesses were studied to assess the effect of varying degrees of COPD on cognitive P300 auditory and visual evoked potentials. The severity of COPD was determined by spirometry with assessment of FEV1, FVC, and FEV1/FVC. Auditory P300 latency was significantly correlated with the FEV1/FVC ratio (Pearson Product Moment correlations r = -.56, N = 20, probability level = 0.1), indicating that increasingly severe airflow impairment is associated with longer auditory P300 latencies. There was no significant association of FEV1/FVC with visual P300 latency or with auditory or visual evoked potential amplitude measures. Progressive impairment of the auditory P300 evoked potential latency occurs with increasing severity of COPD. This impairment is present even in patients with mild COPD, suggesting some degree of accompanying cognitive decline early in the course of COPD with worsening as the disease progresses.