This study examined haematopoietic stem cells of 19 high-risk cases of myelodysplastic syndrome (MDS) for apoptotic and anti-apoptotic signals and cellular proliferation and correlated these with clinical and cytogenetic subtypes, particularly trisomy 8. The aim was to identify cellular and cytogenetic markers of prognostic relevance to survival of high-risk MDS cases. High-risk MDS cases had a significantly higher percentage of apoptotic CD34+ cells and anti-apoptotic survivin+ cells than controls, particularly for trisomy 8 cases. Trisomy 8+ cells showed a significant positive correlation with apoptotic CD34+ cells and capacity for colony formation. The latter was significantly lower in trisomy-8-negative cases than normal controls, while that of trisomy 8 cases was comparable to controls. Our results suggest that although trisomy 8 cells are in a pro-apoptotic state, they are checked by the enhanced expression of anti-apoptotic signals which provide them with their proliferative advantage.