The manufacture of high strength strip products in strip thicknesses less than 1.5mm is very challenging for the conventional hot and cold rolled processing routes. A range of Nb and Nb/V microalloyed steels have been successfully strip cast by the CASTRIP process enabling the development of a range of high strength Ultra-Thin Cast Strip (UCS) products. It was found that the CASTRIP process fully exploits the strengthening potential of the low C-Mn-Nb-(V) alloy design system. Substantial strengthening by microstructural hardening was provided by Nb. Retention of Nb and V in solid solution in hot rolled coils enabled further strengthening by a subsequent age hardening heat treatment. This paper describes the development of a range of high strength low alloy (HSLA) UCS products produced by the CASTRIP process, utilising a low C-Mn-Nb-(V) alloy system, covering yield strengths in the range of 350-550 MPa, in strip thicknesses of 0.9-1.5mm, for both the as rolled and hot dip galvanised coated conditions.