Using the responses of 115 adults attending an asthma educator training course, the Asthma General Knowledge Questionnaire for Adults (AGKQA) was found to be an acceptably valid and reliable measure for assessing knowledge related to the management of asthma by adults. Content and face validity: expert assessors considered the AGKQA to be a relevant and plausible test of the asthma general knowledge content of the programme. Criterion-related validity: the pretraining scores of educators were significantly higher (P<0.001) than those of adults with no experience of asthma; total scores for the AGKQA and an asthma knowledge questionnaire developed for parents of children with asthma correlated strongly, 0.72. Test-retest reproducibility: the Spearman rank correlation for the test-retest score was 0.72 (P<0.02), kappas for concordance of item responses were moderate to very good for two thirds of the items. Internal consistency for the total scale was also acceptable, KR20 0.66. Copyright (C) 2000 Elsevier Science Ireland Ltd.