Dictionary use has played an important role in English learning. Researches showed that dictionary has facilitating effects on vocabulary learning, writing and reading comprehension. However, not all dictionary users can benefit from the use of dictionaries. In fact, dictionary use is not as easy as what we thought, but dictionary skills instruction does not receive much attention in spite of the prevalence of dictionaries. The purpose of this study is to carry out dictionary skills instruction in English classrooms and to assess the effects of dictionary skills instruction on reading comprehension of junior high EFL students in Taiwan. The subjects in the study were 40 second-year junior high students of two classes from Tainan Municipal Cheng-gong Junior High School. Each class was randomly assigned to the experiment group or the control group. The experiment group received dictionary skills instruction in English classes, and the control group did not. First, the 40 subjects were asked to fill out a questionnaire about their dictionary use backgrounds. Then, they were asked to take a pre-test on their dictionary skills and local reading comprehension. After the pre-test, the experimental group received dictionary skills instructions during each class time for about 20 minutes. The instruction lasted about 3 weeks in the beginning of the second semester. Finally, the 40 subjects were asked to take a post-test on their dictionary skills and local reading comprehension. The major findings of the current study were summarized as follws: 1. Generally speaking, among the ten dictionary skills investigated in the current study, junior high EFL students in Taiwan encounter problems more or less. The problems include understanding short forms, labels, and grammar codes of the dictionary, getting familiar with the alphabetical orders, making use of guide words, scanning a dictionary page, distinguishing a homograph, removing regular inflections, removing affixes of derivatives, scanning nearby entries or seeking in the addendum, recognizing compounds or idioms, and finding the right meaning of a polysemous. 2. In addition to these problems, the frequent application of ¡¥Kidrule strategy¡¦ made the situation worse. The participants were very likely to pick any Chinese fragments ¡¥near¡¦ the target words (or other words with similar spellings.) and misinterpret the fragments as the meanings of the target words. 3. Most of the above mentioned problems could be reduced after receiving dictionary skills instruction from their English teacher in a short time. Only the ability to distinguish a homograph can not be improved merely through the teacher¡¦s instruction in a short time. It seems that, to distinguish homographs, the participants¡¦ grammatical knowledge played a more important role than the dictionary skills instruction. As for the using of guide words and the removing of inflections, these two skills can be improved without the teacher¡¦s instruction. 4. According to the study, the use of dictionaries with proper dictionary skills instruction and enough practice could make a significant difference in the performance of local reading comprehension tasks.