Pulmonary cavitation is a well recognized feature of adult pulmonary tuberculosis, but the presence of fluid levels in the cavities has been considered unusual. However, in 550 cases of proven pulmonary tuberculosis in a rural Nigerian population, 257 cases had cavitation, and fluid levels occurred in 56 of the cavities (21%). Positive Ziehl-Nelson sputum stain was more frequent in patients with cavitation and fluid levels: Sputum tests were positive in 69% of those with cavitation and fluid levels, 48% of those with cavitation but no fluid levels, and in 30% without cavitation.