VEGF-A protein concentrations are increased in the serum of HIV-1–positive/KS-negative and AIDS-KS patients. VEGF-A protein concentrations were determined by ELISA in sera of 21 healthy control individuals without a known neoplasm, recent trauma, or surgery (A); in sera of 37 HIV-1–infected patients without KS (B); and in sera of 39 AIDS-KS patients (C). The VEGF-A serum concentration in group A ranged from 35.5 to 347.2 pg/mL, with a mean of 188.6 ± 91.7 pg/mL. Increased VEGF-A serum concentrations were determined in patients of group B, ranging from 26.2 to 634.8 pg/mL, with a mean of 256.7 ± 137.5 pg/mL. The highest VEGF-A serum concentrations were detected in patients of group C, ranging from 87.5 to 835.4 pg/mL, with a mean of 357.1 ± 197.9 pg/mL. The differences in VEGF-A concentrations between groups A and C (P = .001) and between groups B and C (P = .018) were statistically significant as determined by Student’s t-test analysis. The differences between the VEGF-A concentrations of groups A and B were at borderline statistical significance (P = .048).