Jacobs et al。 (1994) carried out an experiment about the effects of L1 glossing, L2 glossing and no gloss on incidental vocabulary acquisition through reading。 85 English speakers who study Spanish in college were selected as subjects。 Divided into 3 groups, the subjects were given some required time to read a Spanish text with English glossing, Spanish glossing and no gloss respectively。 After that, they received an immediate vocabulary test in which the target words were listed。 Then a delayed vocabulary test was carried out 4 weeks later。 The research results suggested that both L1 and L2 glosses were more effective than no gloss。 But there was no significant difference between L1 and L2 glosses。