Abstract Nanocomposites based on unfunctionalized boron nitride nanotubes (BNNT) and polycarbonate (PC) were investigated. BNNT are novel nanoparticles having a tubular structure similar to that of carbon nanotubes except that alternating B and N atoms supersede the C atom. Preparation of the PC/BNNT nanocomposites was carried out at the small scale using dry pre- mixing PC powder and BNNT followed by melt mixing using twin-screw extrusion. The nominal concentration range of BNNT in the PC matrix spans from 0.1 to 5 % in weight. Characterization tasks were carried out on the PC/BNNT samples: morphology observation by electron microscopy (SEM; TEM), rheological measurements (SAOS), thermal characterization (DSC; TGA), tensile mechanical testing, and optical transmittance in the visible range. The rheology data reveal a transition from fluid-like behaviour to a solid like-behaviour at low frequencies as the BNNT content is increased. This result suggests the formation of a percolating structural network of BN nanotubes within the matrix. The interconnected BNNT network results in an apparent yield stress as demonstrated by a plot of viscosity versus shear stress. Linear correlations between optical transmittance, glass transition temperature and loss tangent are demonstrated but need to be investigated further. These correlations may be related to the fact that these properties are all affected by the state of BNNT dispersion and their interaction with the polycarbonate matrix. These and other results will be presented and discussed.