Purpose -The purpose of this paper is to assess the relevance of the glass ceiling effect, according to which the gender log wage gap accelerates in the upper tail of the wage distribution, at the firm level. Design/methodology/approach -The empirical analysis is based on a sample of 4,654 employees, working in a French private company from the Defence and Aerospace sector. Quantile wage regressions were used to study whether a glass ceiling effect exits at the firm level. The difference between the male and female wage distributions is also decomposed into two components, one due to differences in labour market characteristics between men and women and one due to differences in rewards to these individual characteristics. Findings -It was found that the gender wage gap measured through OLS is quite low, less than 8 per cent when controlling for age, experience, qualification and location. It remains rather flat along the wage distribution, a result which casts doubt on the glass ceiling theory. The gender gap is mainly due to differences in labour market characteristics rather than to differences in the rewards of these characteristics, especially among executives. Finally, women face a lower probability of reaching higher hierarchical positions within the firm. Research limitations/implications -Taking into account firm effects matters when measuring the magnitude of the gender wage throughout the wage gap distribution. Originality/value -This paper presents original estimates of the gender wage gap with an unusual, firm-based sample of workers.