The STS debuted as a 2005 model when it replaced the Seville in the Cadillac lineup. The STS is based on the Sigma architecture, which is also the platform for the CTS sedan. The STS styling bears a strong resemblance to the CTS but has a softer, smoother edge to the sharp lines and its own distinct look. The STS name was previously used for the high-performance trim of the Seville. The OnStar advanced communication system is standard on the Cadillac STS.