The aim of this study was to determine flexural properties, water sorption, solubility and release of residual compounds of a new paste type denture base polymer Alldent Sinomer. In addition, an effort was made to reinforce the denture base polymer with a polymer-pre-impregnated glass fibre reinforcement (Stick). Six rhombic test specimens were fabricated for the flexural test in accordance to the ISO 1567 standard. Water sorption and solubility was also determined as described in the ISO standard. Residual compound release into water was determined with the high performance liquid chromatography (HPLC) METHOD: The flexural strength of Sinomer polymer was 85.8 MPa and flexural modulus 2.73 GPa. Storing of test specimens in water reduced the flexural strength and the modulus. By adding the glass fibre reinforcement into the test specimen, the flexural strength and the modulus increased considerably (ANOVA, P < 0.001). The increase was minor with the reinforcement of low fibre content and high with the reinforcement of higher fibre content. Water sorption of the Sinomer polymer was 26.4 microgram mm-3 and solubility was 1.52 microgram mm-3. High performance liquid chromatography analysis revealed the release of 0.18 wt% fraction of compound which was determined as methylmethacrylate (MMA) monomer. The results of this study suggest that the new denture base polymer Sinomer passed the requirements of the ISO standards and that its mechanical properties can be increased considerably by an incorporation of a glass fibre reinforcement. The release of MMA monomer into water from the polymer should be taken into account when the polymer is used in denture bases of patients with an allergy towards MMA.