FISH studies offer the opportunity to supplement standard banded karyotyping by detecting abnormalities in interphase nuclei and clarifying cryptic or complex abnormalities. FISH studies also have limitations, however.18,19 That there are many common genetic abnormalities in MDS/AML requires that multiple FISH probes be scored, leading to increased technologist time and expense. Furthermore, abnormalities that are not specifically targeted by the probes in the panel will remain undetectable if FISH studies are the only mode of analysis. Although several relatively small prior studies3-12 have compared FISH with metaphase cytogenetics in MDS, results are conflicting, and the most cost- and labor-efficient use of FISH as a supplement to metaphase cytogenetics remains uncertain.