We report cases of cave-associated acute pulmonary histoplasmosis that occurred in two Japanese returning from Yucatan, Mexico. Patient 1 is a 35-year-old woman who worked in a bat-infested cave in Mexico for about 3 weeks. Almost all her colleagues had developed cough, fever and headache after 5 days in the cave. She was asymptomatic but her chest radiograph showed multiple nodules 5-10 mm in diameter throughout both lungs. The histoplasmal mycelial-phase complement fixation titer on admission was 1:16, and 1:128 one month later. Patient 2, the 53-year-old husband of patient 1, was also infected by histoplasma in the cave, and similar nodules were observed in his chest radiograph. His histoplasmal complement fixation titer did not elevate. To date, about 20 cases of pulmonary histoplasmosis have been reported in Japan. The number of imported mycoses in Japan is increasing, and histoplasmosis should be considered in the differential diagnosis of pulmonary nodules in travelers returning from endemic areas.