Previous research on the readability of annual reports is based mainly on English narratives and has found them difficult to read. Although the results of such research cannot be generalized to different contexts, accounting narratives written in non-English languages have seldom been analyzed in this respect. More important, few studies have longitudinally examined the evolution in readability of such narratives. This study focuses on the readability evolution of annual report narratives written in Spanish, applying an adapted version of the Flesch readability formula to two sets of documents from different companies over most of the years of the 20th century. The results confirm that the reports are indeed difficult to read but show an improvement in readability over the years. The study tested several variables that might influence readability, including profitability.