Seven morphologists examined 382 slide and 82 non-slide, post-Chernobyl pediatric acute leukemia (AL) cases in radiation-exposed areas of Belarus, Russia and Ukraine; part of a case-control study by the International Consortium for Research on the Health Effects of Radiation. Among the slide cases, 99% were confirmed as AL: 92% acute lymphoid leukemia (ALL) and 86% acute myeloid leukemia (AMD demonstrating the utility of FAB classification for distinguishing ALL and AML. Among the non-slide cases, 79% were confirmed as AL: 84% ALL, and 71% AML. This study affirms AL diagnostic accuracy during a time of social upheaval in the former Soviet Union.