Background: There are few data that link quantified natural rubber latex (NRL) absorbable dusting powder aerosol to biologic responses in NRL-sensitized subjects. Methods: We conducted a study on 30 health care workers with possible occupational asthma. All the subjects but 2 had a positive skin prick test result with NRL extract. Quantified environmental challenge (QEC) with powdered NRL gloves was performed in a 7-m³ chamber. The patients would don and discard a pair of gloves every 3 minutes up to a maximum of 60 minutes. The concentrations of NRL aeroallergen were measured by a competitive IgE immunoassay. Ocular and respiratory symptoms and pulmonary function were monitored. Results: Twenty-six patients (87%) had rhinoconjunctivitis, 19 (63%) had an asthmatic response (responders), and 1 patient developed eosinophilic bronchitis on QEC. The asthmatic responses were of the early type in 15 patients, dual in 3, and isolated late in 1 patient. The duration of exposures sufficient to elicit asthmatic responses varied from 3 to 114 cumulative minutes. Time-weighted average NRL aeroallergen concentrations during QEC with responders ranged between 199 and 1107 ng/m³. NRL concentrations measured at various time points during exposure were reproducible. Measured concentrations of NRL aeroallergen between responders (677 ± 281 ng/m³) and nonresponders (611 ± 351 ng/m³) were not statistically different. The cumulative inhaled NRL aeroallergen dose required for an asthmatic response ranged between 25 to 515 ng. Conclusion: The total dose of latex aeroallergen eliciting an asthmatic response during QEC was mostly affected by the duration of exposure and varied widely from person to person. (J Allergy Clin Immunol 2003;111:788-94