The objective of this prospective clinical usage study was to examine the value of the rule based ‘Therapeutic Assistant’ integrated into an existing Patient Data Management System (PDMS) in helping to prescribe a initial antibiotic regime in accordance with the requirements of accepted guidelines. A prospective study comparing data before and after the introduction of the ‘Therapeutic Assistant’ was carried out. An adequate therapy resulted significantly more often after the introduction of the ‘Therapeutic Assistant’ [p<0.05]; however no difference between the regimes with and without the ‘Therapeutic Assistant’ in the period after its introduction could be established. Whether the ‘Therapeutic Assistant’ influenced the prescriptions made without it will have to be established in a further study.