The purpose of this study was to validate a shortened (11-item) electronic version of the 67-item paper and pencil Environmental Symptoms Questionnaire (ESQ-III) to assess acute mountain sickness (AMS). Thirty-three volunteers (means +/- SE; 28 +/- 1 yr; 74 +/- 2 kg) were given both the paper and pencil and electronic versions of the ESQ (IPAQ 5550, Hewlett Packard, Palo Alto, CA) to complete one after the other at residence altitude (RA) and after 24-h (PP24), 48-h (PP48), and 72-h (PP72) exposure to 4300 m on the summit of Pikes Peak (PP). The AMS-Cerebral (AMS-C) weighted factor score was calculated from responses to the same 11 items for each version of the ESQ. If AMS-C was >or=0.7, then the individual was classified as having AMS. There were no differences in the AMS-C scores between the paper and pencil and electronic versions of the ESQ at RA (0.05 +/- 0.01 vs. 0.05 +/- 0.02), PP24 (0.76 +/- 0.16 vs. 0.74 +/- 0.15), PP48 (0.61 +/- 0.15 vs. 0.53 +/- 0.14), and PP72 (0.34 +/- 0.09 vs. 0.34 +/- 0.09). There were no differences in the incidence of AMS between the paper and pencil and electronic versions of the ESQ at RA (0% vs. 0%), PP24 (33% vs. 36%), PP48 (27% vs. 27%), and PP72 (21% vs. 21%). The relationships between AMS-C calculated from the two versions of the ESQ at RA (r = 0.43; p = 0.01), PP24 (r = 0.92; p = 0.0001), PP48 (r = 0.82; p = 0.0005), and PP72 (r = 0.95; p = 0.0001) were significant. The relationships between the incidence of AMS calculated from the two version of the ESQ at RA (k = 0.90; p = 0.01), PP24 (k = 0.90; p = 0.01), PP48 (k = 0.91; p = 0.01), and PP72 (k = 0.92; p = 0.01) were significant. Our findings suggest that the shortened electronic version can be substituted for the paper and pencil version of the ESQ to assess AMS.