Magnetic relaxation measurements have been performed in the temperature range 300 - 820 K on a cobalt single crystal with [0001] orientation. The relaxation spectrum may be conveniently divided into three regions. Two of these, region I and region II , lie in the hexagonal phase; the third region lies in the cubic phase. In region I we have found a broad relaxation peak, whereas region II is characterized by the complete absence of any relaxation process. In the cubic phase, region III, we have observed a plateau-like magnetic relaxation process having an approximately logarithmic time dependence. An analysis of these relaxation processes is given and they are interpreted in terms of the defects present in the sample.