Abstract Erythrovirus are now classified in three groups: genotype 1 (prototype Pvbaua); genotype 2 (Lali prototype) and genotype 3 (V9 prototype). The role of genotypes 2 and 3 in the development of disease remains uncertain. We have recently showed that those genotypes may represent 50% of the infections in Brazil. The objective of this study is to verify if these viruses are associated with cytopenia of unknown origin. We have designed a case control study in which the prevalence of erythrovirus in the bone marrow sample was compared among cases of cytopenia of unknown origin and 2 controls: bone marrow donors (C1) and, individuals with chronic leukemia (C2). For detection of the virus a nested PCR was performed in bone marrow and plasma samples. Table 1 describes the results obtained in 68 C0, 35 C1 and 67 C2 collected during the year of 2007. The prevalence of the virus in bone marrow was the same in the 3 groups. This result suggests that erythrovirus are common in bone marrow and probably not are responsible for most of cytopenias of unknown origin. A detection of this agent only in bone marrow has little clinical relevance. Table 1. Results obtained during the year of 2007 Cases (C0) Cytopenias Control 1 (C1) Bone marrow donors Controle 2 (C2) Chronics Leukemias Bone marrow Plasma Bone marrow Plasma Bone marrow Plasma positive total positive total positive total positive total positive total positive total 6 (9%) 68 1 (1%) 68 3 (8%) 35 0 35 5 (7%) 67 0 67