This guidance is intended to assist sponsors of investigational new drug applications (INDs) and applicants of new drug applications (NDAs), biologics license applications (BLAs), and supplements to such applications who are planning to conduct clinical studies in neonatal populations. This guidance provides recommendations for neonatal clinical pharmacology studies, whether the studies are conducted pursuant to section 505A of the Federal Food, Drug, and Cosmetic Act (FD&C Act),  section 505B of the FD&C Act, or neither. Effectiveness, safety, or dose-finding studies in neonates involve assessing clinical pharmacology information, such as information regarding a product’s pharmacokinetics (PK) and pharmacodynamics (PD) to inform dose selection and individualization. As such, the general considerations described in this guidance apply to any neonatal studies which incorporate clinical pharmacology assessments. This guidance does not discuss the timing to initiate neonatal studies. Questions regarding the appropriate timing for the initiation of neonatal studies should be discussed with the relevant FDA review division.