对三例钴源事故受照人员照后６ （７） 年和１１ （１２） 年两次细胞遗传学随访结果表明， 两次随访受照者染色体畸变率分别为４２９ ％ 和３６３ ％ ， 均显著高于对照组 （ Ｐ＜ ００１） ， 但两次随访间未见显著差异 （ Ｐ＞ ００５） ， 而且第一次随访染色体畸变是以双＋ 环和无着丝粒断片为主， 第二次随访是以易位、缺失和倒位为主； 两次随访受照者微核率分别为４１７ ‰和１１７ ‰， 第二次随访微核率明显下降（ Ｐ＜ ００１） 。提示随着照后时间推移， 非稳定性染色体畸变逐渐丢失， 稳定性染色体畸变仍保持在较高水平。 The results of two cytogenetic follow-ups of 6 (7) and 11 (12) years after exposure to three cobalt exposure workers showed that the chromosome aberration rates at two follow-up visits were 4.29% and 3.63, respectively %, Both of which were significantly higher than that of the control group (P <001), but no significant difference was found between the two follow-up visits (P> 005) The second follow-up was mainly based on the translocation, deletion and inversion. The micronucleus rates of the two follow-up recipients were 417 ‰ and 117 ‰, respectively. The micronucleus rate of the second follow-up was significantly decreased (P <001). Prompted with the passage of time after the gradual loss of non-stable chromosomal aberrations, stable chromosomal aberrations remained at a high level.