||The paper presents the first phase of research currently under development that is focused on encoding Thonet design style into a generative design system using a shape grammar. The ultimate goal of the work is the design and production of customizable chairs using computer assisted tools, establishing a feasible practical model of the paradigm of mass customization (Davis, 1987). The current research step encompasses the following three steps: (1) codification of the rules describing Thonet design style into a shape grammar; (2) implementing the grammar into a computer tool as parametric design; and (3) rapid prototyping of customized chair designs within the style. Future phases will address the transformation of the Thonet’s grammar to create a new style and the production of real chair designs in this style using computer aided manufacturing. Beginning in the 1830’s, Austrian furniture designer Michael Thonet began experimenting with forming steam beech, in order to produce lighter furniture using fewer components, when compared with the standards of the time. Using the same construction principles and standardized elements, Thonet produced different chairs designs with a strong formal resemblance, creating his own design language. The kit assembly principle, the reduced number of elements, industrial efficiency, and the modular approach to furniture design as a system of interchangeable elements that may be used to assemble different objects enable him to become a pioneer of mass production (Noblet, 1993). The most paradigmatic example of the described vision of furniture design is the chair No. 14 produced in 1858, composed of six structural elements. Due to its simplicity, lightness, ability to be stored in flat and cubic packaging for individual of collective transportation, respectively, No. 14 became one of the most sold chairs worldwide, and it is still in production nowadays. Iconic examples of mass production are formally studied to provide insights to mass customization studies. The study of the shape grammar for the generation of Thonet chairs aimed to ensure rules that would make possible the reproduction of the selected corpus, as well as allow for the generation of new chairs within the developed grammar. Due to the wide variety of Thonet chairs, six chairs were randomly chosen to infer the grammar and then this was fine tuned by checking whether it could account for the generation of other designs not in the original corpus. Shape grammars (Stiny and Gips, 1972) have been used with sucesss both in the analysis as in the synthesis of designs at different scales, from product design to building and urban design. In particular, the use of shape grammars has been efficient in the characterization of objects’ styles and in the generation of new designs within the analyzed style, and it makes design rules amenable to computers implementation (Duarte, 2005). The literature includes one other example of a grammar for chair design by Knight (1980). In the second step of the current research phase, the outlined shape grammar was implemented into a computer program, to assist the designer in conceiving and producing customized chairs using a digital design process. This implementation was developed in Catia by converting the grammar into an equivalent parametric design model. In the third phase, physical models of existing and new chair designs were produced using rapid prototyping. The paper describes the grammar, its computer implementation as a parametric model, and the rapid prototyping of physical models. The generative potential of the proposed digital process is discussed in the context of enabling the mass customization of furniture. The role of the furniture designer in the new paradigm and ideas for further work also are discussed.