We evaluated a Spanish version of the Asthma Opinion Survey (AOS) in a sample of 90 adult Spanish asthma patients. The Spanish AOS showed acceptable internal consistency, and a factorial structure similar to that reported by others, i.e., vulnerability, perceived quality of care, and recognition and control, although we additional ly obtained a fourth factor, attitudes toward patient knowledge. Vulnerability was significantly higher among older patients, and among patients with lower educational level, lower income, and more severe asthma. Perceived quality of care, and recognition and control were positively correlated with frequency of attacks, and recognition and control was significantly higher in older patients. The factor attitudes toward patient knowledge was significantly higher in younger patients and in patients with relatively high income. These results support the cross-cultural validity of this questionnaire.