A highly sensitive urea sensor was developed by incorporating the urease enzyme (Urs) into a polypyrrole film (PPy) in one simple electropolymerisation step, using a sulfonated-beta-cyclodextrin dopant. This PPy-Urs-SCD film has a superior sensitivity of 5.79 mu C mu M-1 and detection in the region of 1.0 x 10(-10) M urea, which is greater than other urea sensors reported in the literature. This is due to the formation of an inclusion complex between urea and a sulfonated-beta-cyclodextrin host in an aqueous solution, which was established using electrochemical techniques. Cyclic voltammetry was used to investigate the effect of an excess concentration of the sulfonated-beta-cyclodextrin on the currents recorded for urea. A clear reduction in the current was observed upon the addition of the sulfonated-beta-cyclodextrin. The formation constant, K-f, was computed as 2745 +/- 300 M-1, indicating the formation of a relatively strong inclusion complex. In addition, a 1:1 stoichiometry for the inclusion complex was deduced from a Job's plot analysis.