Background: In 2005, the Robert Wood Johnson Foundation established the Interdisciplinary Nursing Quality Research Initiative (INQRI) program to produce rigorous evidence regarding linkages between nursing and quality of health care. The purpose of this paper is to describe scientific advances in understanding relationships between nursing, care processes, and the outcomes of the people supported by this discipline in 2004 (year before INQRI’s launch) and in 2009 (5 years after INQRI was established). Methods: Comprehensive literature reviews for the years 2004 and 2009 were conducted using a conceptually based search strategy and multidisciplinary engines. The designs, methods, results, and conclusions of included papers were summarized, synthesized, and analyzed. Results: The literature search identified 389 studies (161 in 2004; 228 in 2009), which examined the relationship between nursing and patient care quality. The number of published papers in all categories of study designs—nonexperimental (72 in 2004; 97 in 2009), quasi-experimental (55 in 2004; 80 in 2009) and experimental (34 in 2004; 51 in 2009)—increased between the years 2004 and 2009. This line of inquiry also has expanded its reach through publications in a greater diversity of journals and journals with higher impact ratings. Discussion: The body of evidence regarding linkages between nursing and quality of care has increased in the nature and depth of science between 2004 and 2009, as seen in higher rates and quality of publications, enhanced methodological rigor, and evidence of stronger interdisciplinary collaboration. Although the unique contribution of INQRI to this expanded body of knowledge is unclear, the evidence supports the increased importance of INQRI’s goal of measuring and enhancing nursing’s contributions to the quality of patient care.