Development of the second-generation LS 400 began after worldwide launch of the first generation under program code 250T. Given the first-generation model's successful reception and high level of customer satisfaction with its design, replicating the original LS 400's attributes with its successor was one of chief engineer Kazuo Okamoto's primary goals (he stated that "a tradition cannot be founded if you reject the first generation"). Externally, the most significant change was an increase in wheelbase length of , resulting in more interior space and an additional of rear-seat legroom. However, as the overall length remained the same, trunk capacity was slightly reduced. The more aerodynamic body ("C""d" 0.28) retained the general profile and contours of the original LS 400 and was the work of the Calty Design Research center in the U.S. Designers had evaluated 20 competing concepts, including several with a radically changed body, before selecting a winning entry in 1991 that included forms and contours similar to the original LS 400. Upon final approval in 1992, an evolutionary redesign was the ultimate result, with new design features consisting of sharper angles, curved body lines, and a beveled grille. More prominent side lines provided a reference point for parking maneuvers, and forward visibility was improved. Production development lasted from 1991 until conclusion in the second quarter of 1994. Design patents were filed at the Japan Patent Office on October 14, 1992 under registration number 732548, using a prototype.