Isolated gain of chromosome 14 (trisomy 14 or +14) has been reported in myeloid malignancy. Seven cases were identified by review of all diagnostic bone marrow specimens with cytogenetics performed at our institution from 1983 to 1995. Median age was older (72 years) and diagnosis was myelodysplasia in the majority of cases. Although trilineage dysplasia occurred, platelet counts were relatively well preserved (median 131 x 10(9)/l). Mosaic karyotype (normal plus abnormal metaphases) was seen in the majority of cases, and survival from diagnosis was short (<2 years). These features are consistent with data from 30 previously published cases, and support the hypothesis that trisomy 14 occurs as a non-random cytogenetic abnormality in association with myeloid malignancy.