Tissue microarray (TMA) is a highly efficient method that allows for large-scale measurement of -expression of RNA or protein in multiple tissue sections simultaneously. Most TMAs are made from paraffin--embedded tissues. In this chapter, we detail a method that enables construction of TMAs from small volumes of cells in suspension. A TMA is built using pellets of 1 x 10(6) to 5 x 10(7) spun cells after fixation, processing, and embedding. The entire procedure is carried out in a microcentrifuge tube and yields excellent preservation of cytomorphology and immunoreactivity from both fresh and frozen suspension cells. It is particularly useful for the study of hematopoietic neoplasms presenting in the blood and bone marrow, fine needle aspirates, and body fluids as well as cultured cells. In addition, this versatile method may facilitate the exploration of gene expression profiling and protein expression in clinical trials where regular tissue biopsies are not available.