This paper reassesses and redefines the concept of equivalence specifically for scientific and technical translation by adopting an approach based on one language pair (English and German) and on one specific text genre, i.e. the research and development report, and type i.e. what Reiss (1971:31-37) calls the 'content-centred' and later the 'informative' text type. The idea is to go beyond the scope of previous investigations in order to identify and describe equivalence-relevant intersubjective regularities in the complex relations between entire source texts and target texts at all textual levels.