Abstract: Compared with β-emitters commonly used in radioimmunotherapy, α-emitters have advantages in high linear energy transfer with a short particle range in tissue resulting in high relative biological effectiveness(RBE) and cytotoxicity. Due to these properties, targeted α-therapy(TAT) is expected to be an effective treatment for disseminate and micrometastatic tumor. In this paper, the recent developments, problems and prospect of ²¹¹At, ²¹³Bi, ²¹²Bi, ²²⁵Ac, and ²²³Ra are discussed.