Abstract A hitherto undescribed hemoglobin anomaly has been detected in a North Carolina Negro family. This new hemoglobin, designated type I, which has been electrophoretically characterized, was found in combination with normal adult A hemoglobin in 6 of 17 members of one family. In each, the ratio of normal to abnormal hemoglobin was similar. Hematologic abnormalities were not observed in any of the affected individuals. Ultracentrifugation sedimentation constants, absorption spectra, solubility and oxygen carrying capacity studies showed no differences from hemoglobin A. It is proposed that the I hemoglobin gene is an allele of hemoglobin A and is transmitted as a simple dominant character in a manner similar to that of sickle cell hemoglobin. The homozygous form of I hemoglobin has not as yet been observed.