Although the literature on the textual properties of scientific discourse is vast, less attention has been paid to the analysis of adjectival frequency in this type of discourse and its semantic implications. Adjectives are a significant communicative tool for scientists, showing the author’s professional persona and manifesting a critical element in the rhetorical properties of research articles. They also allow scientists to describe and qualify phenomena observed during the experimental stage and to anticipate agreements or oppositions to claims with caution and strategical consideration of the opinions and views of peers. Being interrelated with the evaluation and interpretation of data collected in research, adjectives should not be analysed as an isolated phenomenon but within the social and academic environment in which they occur. The purpose of this paper is to explore the frequency and use of adjectives in five advanced scientific texts on biochemistry and to analyse the semantic implications of the observed occurrence. Though limited to five research articles, this study contributes to clarifying the role of adjectives in this type of discourse and underline suggestions as to how to guide students, mainly Spanish-speaking university students, to read and write research articles efficiently.