Read-across (RA) is a popular method for hazard evaluation when in-vivo data are inadequate for chemicals of concern. The Organization for Economic Co-operation and Development (OECD) has investigated the applicability of RA through case studies, and a few of the legislations such as European Union’s Registration, Evaluation, Authorisation, and Restriction of Chemicals (EU-REACH) and regulatory agencies like the US Environmental Protection Agency (US EPA) have already permitted the waiver of new in vivo testing through this process. In recent times, policymaking agencies, academia, and industrial research institutes have collaborated on multi-sectoral cooperative projects to develop and implement new approach methodologies (NAMs) for assessing the toxicological profile of chemicals. The implementation of the new approach methodology was recognized as one of the most significant breakthroughs in increasing the acceptability of the RA technique. NAM data can already be utilized to verify toxicological and chemical similarities. NAM may be used more widely in the future to evaluate the toxicokinetic and hazard characteristics of RA chemicals completely. Examining the completeness of the read-across prediction and the degree of uncertainty in the similarity rationale is among the steps in the uncertainty assessment process that determine if the read-across reasoning is adequate. Globally, scientists are looking to prepare an assessment on the state of the art of RA as a tool for risk assessment for reproducibility of the predicted results, better transferability, and ease of modeling. In this chapter, we have tried to recognize documents on Good Read-Across Practice (GRAP) and best practices to carry out and assess the RA process as relevant sources of guidance to bridge the toxicity data gap rationally.