Ga1-xMnxAs is a new III-V diluted magnetic semiconductor that can be grown by MBE with Mn concentrations up to x ∼ 0.09. Below a critical temperature Tc, determined by the Mn concentration (about 50 K for x = 0.05) the material becomes ferromagnetic. This is attributed to the magnetic long-range order of Mn-hole complexes, the latter being the result of the strong antiferromagnetic interaction between the holes and Mn 3d spins. Transport and magnetic properties of the Ga1-xMnxAs system are strongly correlated. Above Tc, all samples show transport behaviour characteristic for materials near the metal insulator transition. Below Tc, resistivity decreases as the magnetic ordering sets in. When the magnetisation has reached its saturation value (below ∼ 20 K), variable range hopping is the main transport mechanism. Also, a negative magnetoresistance is observed below Tc.