The fracture behavior under tension of notched plates and grooved shafts of polycarbonate has been investigated for a wide range of notch geometries and dimensions of specimens. Careful observations were made on the fracture process at the notch tip during testing. Bluntly notched specimens failed in a fully ductile manner with large shear bands, and sharply notched specimens failed in a brittle manner after the formation of a small crack at the tip of the plastic zone. By varying the notch tip radius and thickness of plates we have been able to clearly distinguish how both influence the brittle-ductile transition. The critical notch tip radius at the brittle-ductile transition increases with increasing plate thickness. Experimental results were discussed in terms of a combination of the maximum elastic stress at the notch tip and the notch tip radius. It has been established that by applying the fracture criterion derived here, we can make an accurate estimate of the strength of notched polycarbonate specimens of any shape or size.