This chapter describes the background to cytogenetic studies in lymphoid disorders other than common acute lymphoblastic leukemia (ALL); these include the less primitive kinds of ALL, such as T-cell ALL and B-cell ALL, all kinds of lymphoma, the chronic lymphoproliferative disorders, and malignant myeloma. Most of these disorders are not as amenable to cytogenetic study as the acute leukemias and chronic myeloid leukemia; the number of published cases is correspondingly fewer, although still greater, so far, than those on solid tumors. It is often not so easy to obtain a sample of the primary malignant tissue, such as lymph node, and the cytogeneticist may have to make do with other, infiltrated tissue, such as blood or bone marrow. Although these can be successful for some types of malignancy, for other types the success rate is very low.