1. Hemolysates of newt (Triturus cristatus) red cells contain four distinct hemoglobin species which have been observed consistently both in individual animals and pooled samples. 2. Hemoglobin heterogeneity in the species arises from existence of multiple hemoglobulins, with no indication of genetic polymorphism. 3. While the relative proportions of the different hemoglobins may vary in different samples, HbII is usually the most abundant, with HbIII and HbIV constituting most of the remainder of the total hemoglobin complement. HbI never exceeds 3-5% of the total hemoglobin. 4. Neither the electrophoretic migration nor the anion exchange properties of the four hemoglobin species are altered by conversion of oxyhemoglobin to the cyanmet derivative, excluding artifacts due to different oxidation states of iron. 5. The average molecular weight of newt total hemoglobulin is 67,182 with no indication of hemoglobin polymers. 6. The use of sulfhydryl-reducing agents (mercaptoethanol, dithiothreitol) as a precaution against aggregation results in extensive degradation of newt hemoglobin through a process similar to "coupled oxidation" by ascorbate. 7. The degradative effects of sulfhydryl-reducing agents on newt hemoglobin suggest that these reagents be used cautiously in any hemoglobin analysis.