Hypocellular myelodysplastic syndrome (MDS) represents only a small portion of MDS, of which, the clinical significance has not been well-defined. By using currently accepted age-adjusted criteria to define hypocellularity as <30% in patients <70 years old, and <20% in >70 years old, we identified 163 (15.5%) hypocelluar MDS from 1049 consecutive adult MDS patients over an 11-year period (1995)(1996)(1997)(1998)(1999)(2000)(2001)(2002)(2003)(2004)(2005)(2006). Compared to normal/hypercellular MDS, hypocellular MDS patients were younger (p < 0.01), less anemic (p = 0.02), but more neutropenic (p < 0.001) and thrombocytopenic (p = 0.05), and had a comparable cytogenetic risk group distribution (p = 0.09) and international prognostic scores (IPSS, p = 0.13). With a median follow-up of 52 months, hypocellular MDS showed a favorable overall survival (56 months versus 28 months, log-rank p < 0.0001) over normal/hypocellular MDS, and this survival preference was also demonstrated in all IPSS groups and cytogenetic risk groups, and was independent of all other risk factors (Cox regression test, p = 0.01). In conclusion, our study demonstrated that hypocellular MDS has characteristic clinicopathologic features, and bone marrow hypocellularity in MDS is an independent factor which predicts a favorable outcome.