Preparation and properties of a new class of diluted magnetic semiconductors (DMS's) based on III-V compounds are reviewed. Epitaxial films of (In,Mn)As and (Ga,Mn)As, the new III-V based DMS's, are now possible by low temperature molecular beam epitaxial growth (<300 °C). The magnetic properties of the epitaxial layers were revealed by the use of the anomalous Hall effect with the assistance of SQUID magnetization measurements. The epitaxial films showed antiferromagnetic, superparamagnetic, and ferromagnetic behaviors depending on the Mn-Mn interaction, which was modified by the presence of carriers and strain in the layers. These new III-V based DMS's will open up new fields in semiconductor technology, where both semiconducting and magnetic properties play critical roles.