Abstract: In the present study we propose a standard model for client loyalty evaluation of services supplied for middle-long periods as banking and assurance services, phone services, gas and electricity supply. In this class of services, the relationship between client and provider lasts until the client shows a clear disloyalty behaviour (switching to another provider or not using the service). We consider two different dimensions of loyalty: behavioural loyalty and attitudinal loyalty which we suggest to analyze in relation to Trust, Convenience, overall Satisfaction and Inertia. The methodology is based on PLS-Path Modelling.