Using large-scale, linked, employer–employee, Finnish panel data, the authors examine firms’ internal versus external hiring decisions more comprehensively than has prior literature. The results show that vacancies in job hierarchies are filled more often by horizontal moves than by promotions. Most horizontal moves are external and within the same job functions, so that internally promoted workers face external competitors occupying higher job levels. Compared to internally promoted workers, external and internal horizontal hires have stronger observable ability indicators (e.g., education, experience, prior work history) but weaker job performance in the year preceding the transfer. Internal and external horizontal hires have similar job histories.