The present paper deals with the Bulgarian translation equivalents of English Noun + Noun Phrases in science and technology texts. The scope of the data is restricted to NPs because their contextual dependence raises a number of issues associated with translation practices. Another reason is that Bulgarian and English greatly differ with regard to premodification. This leads to employing transformations which usually make the meaning more explicit. With view to finding out the source of the greater explicitness in the translations, the source language structures are compared with the target language structures produced by translators and then with similar structures in Bulgarian texts. The data is excerpted from a corpus of English-Bulgarian translations. The aim of the study is to investigate the transformations employed by translators to render English N+NPs .