Companhia Siderúrgica de Tubarão (CST) has been making intensive efforts to increase the slab production and to maintain a stable level of 5.0 million tons/year. In order to achieve these objectives, it is essential to consider the ability to produce narrow width slabs, 750 ~ 1,050 mm, using twin casting technology. This paper describes the main aspects associated with CST's twin casting process, operational and quality problems faced during the first heats produced, as well as the action plan used by CST to overcome these problems.