This paper describes the results of an experimental and analytical study of the effect of specimen size on the fracture-toughness behavior of A36 steel, primarily in the lower-transition region.This region is beyond the limits of plane-strain as defined by ASTM E-399, but in the region where failure occurs prior to any macroscopic fibrous tearing. Experimental results were obtained using Crack-Tip Opening Displacement (CTOD) three-point bend specimens, and analytical results were obtained using a 3-D elastic-plastic finite-element analysis.Two specimen sizes, full thickness [31.8-mm (1.25-in.) thick] and reduced thickness [12.7-mm (0.50-in.) thick], were investigated using the preferred t X 2t X 8t specimen size.