Embryo fetal development (EFD) studies in nonhuman primates are frequently conducted in macaques with Macaca fascicularis (cynomolgus monkey, long-tailed macaque, crab-eating macaque) being the most accepted model. EFD studies are also feasible in the marmoset. Due to recent guideline changes (ICH M3(R2) and S6(R1)), EFD studies are largely confined to conventional pharmaceutical compounds rather than biopharmaceuticals. This chapter describes basic study designs and provides working protocols for collecting, processing, and staining fetuses, including collection of amniotic fluid and umbilical cord blood. The chapter also covers the examination and terminology for external, visceral, and skeletal examinations of fetuses. The species covered in this chapter are cynomolgus monkey (long-tailed macaque) and marmoset monkey.