The majority of acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS) patients reported with chromosome 16 abnormalities had the inv(16)(p13q22) or t(16;16)(p13;q22) rearrangements, which were associated with a favorable prognosis. In contrast, del(16)(q22) was reported less commonly but was associated with a less favorable prognosis. We describe an 80-year-old woman who presented with MDS (refractory anemia). Chromosome analysis from bone marrow aspirate cultures showed monosomy 16 as the sole cytogenetic abnormality. Comparison of this patient with previously reported cases of monosomy 16 showed that this uncommon abnormality was associated with myeloid disorders. Monosomy 16 patients, similar to del(16)(q22) patients, tended to be elderly, presented with MDS or AML, and had a poor prognosis. The similarity in clinical course for del(16)(q22) and monosomy 16 patients suggests that the phenotype in both groups resulted from loss of important gene(s) on 16q, as distinct from the fusion gene product identified in the inv(16) and t(16;16) rearrangements.