Adult cat fleas, Ctenocephalides felis (Bouché), survive and reproduce when fed human blood through an artificial membrane system. When a dog hair substrate was included in cages with the fleas, mean adult mortality was 2.4 after 12 d of bloodfeeding. Egg production began after 3 d and was continuous for 12 d, ranging from 3 to 4 eggs per female per day. In cages without hair, mean adult mortality was 61.2% after 12 d of bloodfeeding. Egg production began after 2 d, reached a maximum of two eggs per female per day after 7 d, and decreased thereafter. No significant differences in egg hatch were seen in treatment groups sampled from 5 to 7 d after the onset of bloodfeeding. After 7 d, however, egg hatch for fleas maintained in cages without hair was significantly lower than in cages where fleas were maintained on dog hair. Adult emergence from these larvae did not differ significantly between the two groups. Egg hatch and adult emergence in both groups of fleas fed on human blood did not differ significantly from egg hatch and adult emergence in fleas fed on colony cats.