The development of biological products has experienced continuous growth over the past three decades. The expiration of patent protection for many biological medicines has led to the development of biosimilars in many countries around the world. This paper reviews the literature on biosimilar drugs and covers their therapeutic status, clinical trials, approved biosimilars, and regulatory guidelines in Japan, South Korea, and Malaysia. The literature suggests that biosimilars are comparable but not identical to the reference product. They are not a generic version of an innovative product and do not ensure therapeutic equivalence. Biosimilars present more challenges than conventional generics and their marketing approval is also much more complicated. Guidelines for biosimilars were published in Japan in July 2009 by the Ministry of Health, Labour and Welfare (MHLW), in South Korea in March 2009 by the Ministry of Food and Drug Safety (MFDS), and in Malaysia in July 2008 by the National Pharmaceutical Control Bureau (NPCB).