The objective of this study was to determine the level of adherence of pediatricians in Spain to the Spanish National Guidelines for Asthma Treatment with regard to the use of a peak flow meter (PEFR) or a spirometer in the diagnosis and management of asthma in childhood and to analyze sources of variations in these practices. A prospective survey (consisting of demographic and asthma knowledge sections) was conducted over a 2-wk time interval of 3000 pediatricians throughout the country. At least one part of the questionnaire was completed and returned by 2773 individuals (92.4%), with 2347 (78.2%) answering both sections; results are for this population. Around 62% of the pediatricians reported having a peak flow meter or a spirometer in their office; however, only 33% and 48% of them used the devices for the diagnosis and treatment of asthma, respectively. There was a significant association between being older (36-55 yr old) and using PEFR or spirometry for the diagnosis (OR: 1.35,