This paper analyses the discourse of science through the study of collocational patterns of high frequency noun keywords in science textbooks used by upper secondary students in Malaysia. Research has shown that one of the areas of difficulty in science discourse concerns lexis, especially that of collocations. This paper describes a corpus-based analysis of the lexical collocations, specifically the noun/noun (NN), noun/adjective(AN) and verb/noun(VN) combinations, of high-frequency noun keywords in this science corpus. The study found that the NN and AN syntactic combinations were the more predominant combination type among the collocations of the noun keywords. Most of the collocations have been found to fall into the category between free and restricted combinations. In addition, the analysis have also uncovered clusters of overlapping collocations which show a tendency towards the free end of the restricted category of combinations.