A girl with Bloom's syndrome is reported. We have not found chromosomic or inmunoglobulin alterations, in opposition to described by other. We remark, for the first time in medical literature, a deficit of GH secretion without response to several stimulus. The other hormonal explorations were normal. We don't know if, that finding will be of pathogenic importance for the stunted growth of Bloom's syndrome or this is a casual association. Anyway, the good therapeutic results with the exogenous human growth hormone administration, is of a great interest for the investigation of pituitary GH reserve in any case of Bloom's syndrome.