Introduction: Inhaled medication is the cornerstone of pharmacological treatment for chronic respiratory diseases. Therefore, it is important to use a metered-dose inhaler (MDI) correctly to get the appropriate dosage and benefit from the drug. Health-care workers (HCW) are responsible for teaching the correct MDI technique. Unfortunately, numerous studies consistently show that HCW have poor MDI technique. This study aimed to evaluate the current knowledge of MDI technique in HCW working in three general hospitals. Material and methods: A hospital-based, cross-sectional descriptive study was conducted in three general hospitals in Aguascalientes, México. Three surveyors simultaneously scored through a 14 dichotomic questions list as bad, regular, good, and very good MDI technique. Data were analyzed with SPSS version 16. Statistical analyses were performed using chi-square test or unpaired t-tests. An analysis of one-way ANOVA was used for comparison of three independent general hospitals. Values of p < 0.05 were considered to indicate statistical significance. Results: A total of 244 HCWs were surveyed: 78.3% were nurses whereas 21.3% were physicians. The inter-observer concordance analysis among observers was 0.97. We observed that 32.4% (79) performed a bad technique, 51.6% (126) a regular technique, 13.5% (33) a good one, and 2.5% HCW (6) a very good technique. No difference between gender, labor category, schedule, service, age, seniority, and education degree between the three hospitals was observed. The most common mistakes were "insufficient expiration prior to activation of the device", and "the distance the inhaler was placed for inhalation" (83 and 84% respectively). Conclusion: We observed that a high percentage of HCW do not follow the MDI technique correctly, being this percentage even higher than the reported in other studies. These observations suggest the urgent need to establish frequent training programs for the correct use of MDI.