Introduction: The article presents the results of a study on scientific collaboration between Spanish universities and private enterprise, measured in terms of the co-authorship of papers published in international journals. Method: Bibliometric analysis of papers published in journals listed in Scopus in 2003-2011. Indicators were calculated for output, collaboration, standardised impact and publication in highly reputed journals. Analysis: A number of dimensions were explored: (1) publication patterns among domestic companies; (2) subject matter distribution and impact of the papers published; (3) university-company partnering based on papers co-authored by university and private sector researchers; and (4) regional differences. Results: The three fields where production was most intense were biochemistry, genetics and molecular biology, engineering and medicine. Research in collaboration with companies had a lower normalised impact than research conducted by universities alone. The highest volumes of private sector collaboration with Spanish universities were recorded for pharmaceutical companies. Conclusions: Companies' output was observed to decline across the period studied and their academic articles appeared to be less visible than the papers published by other institutions.