The objectives of this study were (a) to compare the CD4+ lymphocyte profiles over time of two groups of patients hospitalized for tuberculosis (TB) treatment [a group of patients with TB only (TB group) and a group dually infected by HIV and TB (HIV/TB group)] and (b) to assess the usefulness of the total lymphocyte count (TLC) as a surrogate of the CD4+ lymphocyte count in the HIV/TB group. A total of 345 patients were enrolled in the study of whom 104 (29.8%) were HIV seropositive (HIV/TB). On admission, the CD4+ lymphocyte counts of the HIV/TB cohort were significantly lower than the TB group with medians of 230 (interquartile range, 90-475) and 630 (500-865), respectively (p < 0.0001). The CD4+ lymphocyte count increased significantly in both cohorts on routine TB treatment. A TLC of 1,300-1,500 cells/mm3 was found to be predictive of a CD4+ lymphocyte count of < or = 200 cells/mm3 both on admission and after 1 month of TB therapy. We conclude from this study that the positive influence of TB therapy on the CD4+ lymphocyte count strongly suggests an additional avenue of influence on the course of HIV infection, whereas the usefulness of the TLC as a surrogate estimation of CD4+ lymphocyte count in HIV/TB patients has important implications for the developing world.