This study aims at analyzing the gender gap in salaries observed in Spanish public universities. It focuses on the glass ceiling problem and quantifies its importance in the gender earnings gap. This article shows that most of the gender earnings gap observed among the faculty of the University of Murcia is due to a glass ceiling problem in accessing the rank of Full Professor, and it includes a measure of research productivity in the analysis. Despite increases in the number of women promoted to the level of Full Professor has increased in recent years, women still comprise less than 30% of the total faculty at this academic rank. The second most important variable that explains most of the earnings gap is research productivity.