J-R curves were determined for five materials (7075-T651, 2024-T351, HY130, HY80, and A723, Class 1, Grade 4) using precracked Charpy specimens and standard size C(T) and SE(B) specimens. Crack growth in the Charpy specimens was estimated using the “load drop” method of analysis of the load-displacement trace, and crack extension in the C(T) and SE(B) specimens was determined using the electric potential method. The results show that physical crack extension in the larger specimen was not well estimated by the Charpy specimen results. If the crack extension is presented as relative crack growth (as a percentage of the uncracked ligament), however, the agreement between the two widely different specimen sizes is much better, although not exact. Except in the relatively brittle 7075-T651, the J corresponding to 0, 1%, and 2% crack growth was higher in the Charpy specimens than in the larger specimens. This was attributed to the inability of the “load drop” method to determine the exact location of the crack initiation. Although nonconservative, we believe the “load drop” method analysis of precracked Charpy data is adequate for quality control toughness testing, provided it is realized that JIc and J-R curves may be overestimated slightly.