Conventional product development process employs a design-build-break philosophy. The sequentially executed product development process often results in a prolonged lead-time and an elevated product cost. The proposed concurrent design and manufacturing (CDM) process employs physics-based computational methods together with computer graphics technique for product design. This proposed approach employs Virtual Prototyping (VP) technology to support a cross-functional team analyzing product performance, reliability, and manufacturing cost early in the product development stage; and conducting quantitative trade-off for design decision making. Physical prototypes of the product design are then produced using Rapid Prototyping (RP) technique primarily for design verification purposes. The proposed CDM approach holds potential for shortening the overall product development cycle, improving product quality, and reducing product cost. A software tool environment that supports CDM for mechanical systems is being built at the Concurrent Design and Manufacturing Research Laboratory (http://cdm.ou.edu) at the University of Oklahoma. A snap shot of the environment is illustrated using a two-stroke engine example. This paper presents three unique concepts and methods for product development: (i) bringing product performance, quality, and manufacturing cost together in early design stage for design considerations, (ii) supporting design decision-making through a quantitative approach, and (iii) incorporating rapid prototyping for design verification through physical prototypes.