Neural stem cells were isolated from postnatal Jag1^tmVtlr or Notch1^tm2Agt animals carrying the Cre-reporter Rosa26R allele. Inactivation of the floxed allele in dissociated cells was accomplished using an Adenoviral-Cre vector. The Jagged1- or Notch1-deficient cells were able to form, at similar rates, neurospheres that were indistinguishable in size and morphology from those formed by control cells. 5 days post-ablation, a 5-fold or 250-fold reduction in self-replicating stem cells was detected for Jagged1- or Notch1-deficient neurospheres. Differentiation potential was not affected for either Jagged1- or Notch1-deficient neural stem cells in culture. Similar results were found for neural stem cells isolated from the subventricular zone of adult mice carrying floxed Jagged1 or Notch1.