Standard techniques of karyotypic analysis of bone marrow or peripheral blood cells generally use large numbers of cells. Thus, the quantity of cells harvested from one bone marrow or blood puncture frequently represents a limiting factor for other assays such as molecular biology or flow cytometry, which are often essential for the diagnosis of hematological diseases. To resolve this problem, we developed a "miniaturized technique" of cytogenetic analysis that we tested on bone marrow (BM) cells from 20 patients with multiple myeloma (MM), 5 patients with acute leukemia (AL), as well as on CD34+ cells purified from the blood of 8 patients with agnogenic myeloid metaplasia (AMM). We used 3 x 10(6) BM cells from MM patients (for testing 6 different culture conditions), 10(6) BM cells from AL (2 culture conditions) and 4 x 10(3) CD34+ cells from AMM patients. In most patients, 20 good quality metaphases per slide were easily analyzed, showing that a 10-40 times reduction of the number of cells used for cytogenetics allows a reliable karyotypic analysis in hematological malignancies.