Fundamental issues and engineering application aspects of Pressure-Assisted Injection Forging (PAIF) of thick-walled tubular components were studied experimentally and analytically. Achievements from this study met its pre-defined goals and are demonstrated with the following facts: Pressurising materials were selected and qualified under six different loading conditions, based on which a simplified configuration for confined compression tests was proposed, and particularly, a unique biaxial testing machine was developed and used satisfactorily. The test data were subsequently used to establish constitutive descriptions of the materials and to facilitate the FE modelling to simulate the forming processes. An upper bound analysis of Pressure-assisted injection forging of thick-walled tubular components with hollow flanges was conducted and formulated solution for the forming process was developed, by which the maximum forming-force for a given component geometry can be predicted w ith sufficient accuracy. Failure modes and process range for pressure-assisted injection forging of thick-walled tubular components were studied experimentally and numerically, as a result, eight standard failure forms were categorized and three forming limit diagrams were established, which were validated experimentally and can be used as a guidance for the process design. By combining above results achieved, an approach for synthesising concurrent design and manufacture of thick-walled tubular components with pressure-assisted injection forging was developed, in which technical details of the process and step by step procedure towards producing sound tubular components were provided. The development represents a significant progress towards engineering and industrial applications of the pressure-assisted injection forging (PAIF) technology. Using the forming limit diagrams as a design guideline and following the approach for synthesising. concurrent design and manufacture, an engineering component - hollow gear shaft was formed successfully.