AbstractWe have studied the carrier state of the Hunter syndrome using a series of obligate carriers, females at high genetics risk, and normal control women. Specific odds of a female being a carrier of Hunter syndrome were based on serum levels of iduronate 2‐sulphate sulphatase activity. These, together with the prior genetic odds, may be used in calculating the overall odds of a woman being a carrier. Iduronate 2‐sulphate sulphatase levels were found to increase significantly with age. Obligate carriers from families of severe cases had significantly lower enzyme levels compared with those from families of mild cases. In contrast, enzyme levels in sera of mild and severe cases were not significantly different. With the accumulation of more data the effect of age of the potential carrier and the severity of the disease may have to be taken into consideration in the risk calculation.Hair‐root analysis was more reliable in the detection of carriers than estimation of serum enzyme levels, but some individuals could not be classified with confidence by hair‐root analysis alone. Carrier detection was most reliable when hair‐root analysis and serum enzyme levels were taken together.