A male infant of three month presented with recurrent mucosal and fungal infections, diarrhoea and failure to thrive from the age of three weeks. Laboratory test revealed T-B-NK + severe combined immunodeficiency (SCID). Family history and immunolaboratory findings suggested autosomal recessive form of the disease. Haploidentical maternal bone marrow transplantation (BMT) was carried out at five and half months of age. Over the two years after BMT, the patient's somatomotoric and mental development is normal. Cellular immune responses and the substantial immunoglobulin production suggest immunoreconstruction in the child born with complete lack of adaptive immunity. According to the author's knowledge, this is the first T-B-NK + patient in Hungary, whose disease was diagnosed and adequately treated in infancy.