This paper presents experimental results relating to the perceived usability of automated telephone services which incorporate a spoken language dialogue interface. Using a new Wizard of Oz experimental technique, users' attitudes towards automated telephone services are measured by a Likert attitude questionnaire. Factor Analysis performed on subjects' responses to the questionnaire produced a set of five underlying group factors which accounted for 74% of the variance in the questionnaire scores. On the basis of the factor analysis, a multiple regression model was constructed using the highest loading attributes on each of the five factors. The predictive power of this model was assessed.