This study investigates vocabulary learning strategy (VLS) preferences of lower and higher proficiency Japanese university science students studying English as a foreign language. The study was conducted over a 9-week period as the participants received supplemental explicit VLS instruction on six strategies. The 38 participants (14 males and 24 females) were all first- and second-year students majoring in life sciences. The explicit vocabulary instruction focused on three cognitive, or shallower, strategies (vocalization, writing rehearsal, and word cards) and three memory strategies involving deeper processing (imagery strategies, association, and mnemonics). The aim of the study was to see which VLSs the learners were familiar with; their perceptions of VLSs for learning general academic vocabulary and for learning science words; and finally, after instruction, which strategy the learners preferred. Statistical analyses and qualitative data (student comments on each of the six strategies) were used to answer the questions. The results shed some light on the VLS preferences of life science students for studying both types of words. It also confirms the value of explicit VLS instruction for both lower and higher proficiency students and increased the researchers' understanding of the students' vocabulary learning behavior.