The outcome of a life cycle assessment (LCA) is heavily reliant on the input data acquired during the life cycle inventory (LCI), the approach utilized to construct the LCI, and the methods used to develop the life cycle impact assessment (LCIA). LCI is generally developed using either a process or input-output (I-O) approach; both techniques have advantages and disadvantages. The main shortcoming of the process model is the subjectivity and inconsistencies of boundary selection, whereas the 1-0 method produces highly aggregated results. Additionally, neither typically incorporates uncertainty. By combining the two methods into a single framework the best aspects of each inventory approach are developed, while the weaknesses are minimized. Two case studies, corn production and on-site construction processes, are presented to demonstrate the advantages and disadvantages of LCA approaches. Although seemingly different, the case studies exemplify the use of hybrid LCA for disparate systems. The on-site construction case study explores the differences between process, I-O, and hybrid inventories. The corn production case study focuses on uncertainty in the inventory and impact assessment stages of LCA.