Abstract: In the past years the SHARP EL-5100 calculators and the CASIO series calculators have being used fo restim ation of KT₅₀、LC₅₀ and LD₅₀ based on the probit analysis method in the bioassay of insecticide. There is a sharp rise in the computer ueage in the recent years. The calculation of KT₅₀. LC₅₀ and LD₅₀ valus can be simplied through use of a computer. The computer program in BASIC presented in this paper was developed in 1989 and run in SHARP PC-1500 and CASIO FB series computers and IBM PC compatible With this program, the KT₅₀. LC₅₀ and LD₅₀ and its associated 95% intervals, the slope value of the dose/effective carve, and theΧ² are automatically generated.