Real time observations of submicrometre scale failure mechanisms of injection moulded multiphase blends are extremely difficult to perform. This has been accomplished using a specially designed tensile fixture and sample preparation techniques for a polycarbonate-polyester blend. Blunt or sharp cracks could be developed in the blend which were dependent on the shape of the polyester domains. Their initiation and propagation mechanisms have been examined at the submicrometre and bulk scales. The failures observed in the thin-sections were similar to failure mechanisms observed in the bulk.