The pharmacokinetics of cyclophosphamide was studied in 10 Kenyan Africans with Hodgkins lymphoma. The mean +/- s.d. elimination half-life (t1/2) was 7.5 +/- 1.38 h. The mean +/- s.d. volume of the central compartment (V1) was 0.35 +/- 0.12 l/kg and the apparent volume of distribution (V) was 0.64 +/- 0.06 l/kg. The microconstants k21, k12 and k10 were 1.81 +/- 0.84 h-1, 1.90 +/- 1.080 h-1 and 2.05 +/- 0.86 h-1 respectively (mean +/- s.d.).