Chromosome 1 is the largest human chromosome and contains over 1600 known genes and 1000 novel coding sequences or transcripts. It is, therefore, not surprising that recurrent chromosome 1 abnormalities are regularly encountered in both neoplastic and non-neoplastic medical conditions. The current review is focused on myeloid malignancies where we summarize the relevant published literature and discuss specific karyotype-phenotype associations. We show that chromosome 1 abnormalities are most frequent in BCR-ABL-negative classic myeloproliferative neoplasms (MPN): polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofibrosis (PMF). Specific abnormalities include duplications (e.g. 1q12-->1q32 in PV, 1q21-32-->1q32-44 in post-PV MF or PMF), deletions (e.g. 1p13-36-->pter in PV or PMF, 1q21 in PMF) and unbalanced translocations involving chromosome 6, such as der(6)t(1;6)(q21-25;p21.3-23), and other partner chromosomes involving 1q10/1p11 and 1q21-25 breakpoints. Although occasionally seen in chronic phase MPN, unbalanced 1;7 translocations, e.g. der(1;7)(q10;p10), are usually seen in acute myeloid leukemia (AML), myelodysplastic syndromes (MDS), and post-MPN AML/MDS. These observations suggest that certain chromosome 1 regions, especially 1q21-1q32 and 1p11-13, might harbor oncogenes or tumor suppressor genes that are pathogenetically relevant to both chronic and advanced phases of MPN.