Disclosed are agonist anti-CD40 molecules, including monoclonal antibodies, which can bind to and stimulate professional and non-professional human antigen-presenting cells ("APCs"), enhance the stimulatory effect of CD40L on CD40 positive cells and/or induce phenotypical maturation of monocyte derived dendritic cells. Several such monoclonal antibodies are provided, and cell lines producing them have been deposited at the American Type Culture Collection.