Kawasaki Heavy Industries launched the first model of L20A gas turbine, rated at 18MW, in 2001 [1]. After the first model was launched, continuing improvements in both performance and durability have been made [2]. This paper describes the latest improvement activities, including cooling improvement of the 1st stage turbine blades using the results from an optical pyrometer thermal mapping system (Rotamap II) and performance improvements achieved by reducing the secondary air flow. In addition, by applying the non-cooled 2nd stage turbine blades made of single crystal material, plus improved rim sealing structure, cavity temperature was kept below the desired limit with a reduced amount of cooling air being required. KHI also developed a L20A “STEAM INJECTION” version. This system enables the utilization of the variable surplus steam of a cogeneration plant to increase the electric output. This paper describes the test result of L20A model gas turbine with steam injection capabilities. In the test, performance and emissions were measured as usual, but in addition, metal temperature of 1st stage blade was measured using the pyrometer system in order to confirm the propriety of the TIT de-rate schedule which keeps the metal temperature at the same level as the L20A “NORMAL” version under the steam injected condition.