We report herein a 38-year-old male patient with Fanconi anemia but with few phenotypic manifestations--short stature, sterility, and hypoplasic anemia with several years of evolution-who developed a myelodysplastic syndrome (MDS). Bone marrow karyotype showed long arm triplication of chromosome 1 (q12-21q31-q32), and two markers add(11)(p15) and add(21)(q22) which had extra material of chromosome 3 besides the normal chromosome 3 pair. Peripheral blood showed chromosome instability; SCE was normal. Both the patient and his family showed a high prevalence of malignant diseases. 1q duplication and, in a few cases, triplication of 1q has been related to Fanconi anemia, being of unknown significance.