The invention provides cells and methods of using the cells for the propagation of replication-deficient adenoviral vectors. The cells comprise at least one heterologous nucleic acid sequence which upon expression produces at least one non-adenoviral gene product that complements in trans for a deficiency in at least one essential gene function of one or more regions of an adenoviral genome so as to propagate a replication-deficient adenoviral vector comprising an adenoviral genome deficient in the at least one essential gene function of the one or more regions when present in the cell.