This paper describes a study investigating the use of three types of dictionaries by deaf (i.e., with severe to profound hearing loss) high school students while reading to determine the effectiveness of each type for acquiring the meanings of unknown vocabulary in text. The dictionary types used include an online bilingual multimedia English-ASL dictionary (OBMEAD), a paper English-ASL dictionary (PBEAD), and an online monolingual English dictionary (OMED). Results indicate that for immediate recall of target words the OBMEAD was superior to both the PBEAD and the OMED. For later recall, no significant difference appeared between the recall for words learned via use of OBMEAD and PBEAD. Recall for each of these was statistically superior to recall for words learned via OMED. (Contains 7 figures and 1 table.) [This paper was published in: "American Annals of the Deaf," 157(4), xx.]