This document provides information about the 4th THz-Bio Workshop to be held February 14-15, 2013 in Seoul, Korea. It will be co-organized by the Center for THz-Bio and KAERI WCI Center for Quantum-Beam-based Radiation Research and supported by the National Research Foundation of Korea. The workshop will include sessions on THz instrumentation, THz bio interaction, and THz bio imaging with speakers from various universities and research institutions from Korea, Japan, China, Germany, Italy, Russia, and the USA. It provides key dates and registration fee information as well as contact details for workshop chairs and managers.