This report is intended to provide an up-to-date overview of the lymphoid and hematopietic diseases induced in humans and rodents following exposure to chemical agents. It includes a brief introduction to hematopoiesis and lymphopoiesis in humans and rodents, selected characteristics of known leukemia-inducing agents and their effects in mice and rats are compared and the value of rodents models. Six different classes of established leukemia-inducing agents were included: in ionizing radiation, alkylatingagents, epipodophyllotoxin-type topoisomerase inhibitors, dioxopiperazine-type topoisomerase inhibitors, benzene, and 1,3 butadiene. The current understanding of mechanisms underlying acute nonlymphocytic leukemia in humans and thymic lymphoma and myeloid leukemia in mice is presented. The relevance of mouse models for human leukemias and lymphomas is discussed. Furthermore, chronic animal bioassays using mouse models have been shown to be effective in identifying human leukemia-inducing agents.