Because Japanese high school graduates have poor basic English skills they have difficulty acquiringduring the 6 years of medical school English skills sufficient to write medical papers in easily understood English and to converse with foreign medical researchers at international medical conferences in fluent English. In an attempt to improve English teaching in medical schools we analyzed the structures of sentences in high school English textbooks and compared them with those of sentences in more advanced English, as in the journals Science and Nature. We found that the English in high school textbooks has significantly lower subordination ratios. Thus, we propose that English with higher subordination ratios be taught in the 1st year of medical school.