The FDA guidance focuses on the use of the NOAEL to establish the maximum recommended starting dose. The majority of NOAEL has been described inaccurately or incompletely in final reports for 90-days repeated dose toxicity test based on GLP (good laboratory practice) regulation. This is the most serious one of reasons for why most pharmaceutical companies targeting global markets have disregarded the final report produced from GLP facilities in Korea. The problems in deciding NOAEL reflected in the final reports are mainly due to the followings; 1) Inaccurate description or use of NOEL, NOAEL and LOAEL, 2) Insufficient and inappropriate interpretations in findings from toxicity test. This paper is intended to provide the insight into distinguishing NOAEL from NOEL and LOAEL, and into classifying findings from toxicity test. Here, the three step method is newly suggested by applying the weight-based classification to the NOEL, NOAEL and LOAEL based on the findings.