Ethnic aspects of cord serum alpha 2-macroglobulin levels in Chinese, Caucasians and Ghurkas in Hong Kong. Serum alpha 2-macroglobulin (alpha 2-M) levels were measured in cord sera of Chinese, Caucasian and Ghurka babies in Hong Kong by the antibody-agar radial immunodiffusion technique. The values for male babies of the three ethnic groups were 293 +/- 59, 323 +/- 79 and 303 +/- 72 mg./100 ml., respectively; those for female babies were 287 +/- 74, 315 +/- 74 and 317 +/- 7) mg./100 ml., respectively. Although a general similarity of cord serum alpha 2-M levels was evident at birth, it was noted that ethnic differences in the level of this serum protein only become apparent later in life. The value obtained for Caucasian cord serum alpha 2-M in Hong Kong was significantly lower than a published value for Caucasians elsewhere.