a b s t r a c tBackground: Microwave-based devices target sweat glands through energy delivery at the dermal esubcutaneous interface. These devices have been approved by the Food and Drug Administration as a noninvasive treatment for axillary hyperhidrosis. Treatment for osmidrosis has only been reported in one preliminary study. Objectives: To investigate the efficacy, safety, and histological changes of the microwave-based devices in treating axillary osmidrosis. Methods: We conducted a prospective study in a tertiary referral center in Taiwan. Patients with axillary osmidrosis were recruited and received two consecutive treatment sessions with a 3-month interval. Skin biopsy was obtained to evaluate histological changes. The efficacy was determined by odor reduction using a patient reported 10-point odor scale. Responders were defined as participants with a reduction of at least 3 points of the Odor-10 score at their 90-day follow-up visit. Results: Seven patients were enrolled. Mean reduction of odor was 61.8%. Six patients met the primary endpoint of odor reduction. Skin biopsy specimens reveled 93% reduction of apocrine glands. Histopathological changes include dermal fibrosis, necrosis of sweat glands, and subcutaneous fat necrosis. Transient swelling, bruise, numbness, lumps, and hypotrichosis were possible side effects. No patient reported disabling side effects. Conclusion: Microwave-based devices are noninvasive and a potential alternative therapeutic modality for axillary osmidrosis treatment.