On April 22, 2021, Japan’s Ministry of Health, Labour and Welfare (hereafter referred to as MHLW) issued a technical guidance for single dose toxicity assessment of quasi-drugs and cosmetics. In this document, MHLW summarizes the process of evaluating single dose toxicity evaluation by Weight of Evidence (normally abbreviated as WoE) combining safety data including data from 3T3-NRU cytotoxic test.