Guatemalan patients with onchocercal nodules will be enrolled in an open label trial with four treatment groups: Group A (rifampin 20 mg/kg by mouth [po; maximum 600 mg/day]); B (azithromycin 12 mg/kg po [maximum 500 mg/day]); C (combination of rifampin 20 mg/kg po [maximum 600 mg/day] and azithromycin 12 mg/kg po [maximum 500 mg/day]); D (control group, multivitamin). At the end of the five day treatment course all participants will receive a single dose of ivermectin (150 mcg/kg).