A method of controlling the functioning of a portable medicament dispenser, said portable medicament dispenser being for use with a refill container, said method comprising: (a) providing a memory for storing one or more parameters relating to the functioning of said dispenser; (b) storing authentication data for authenticating data for controlling a function of said dispenser; (c) receiving control data for said dispenser; (d) performing authentication of the control data using said stored authentication data; (e) in dependence on a result of the authentication, activating one or more parameters in said memory to control functioning of said dispenser in accordance with said control data, characterized in that the step (d) of performing authentication of the control data is performed by said refill container.