It is a general belief that the English /si/ and /?i/ are problematic for Japanese ESL learners. This study examines whether monolingual Japanese speakers distinguish [si] and [?i] in both perception and production and what are the sources of Japanese ESL learners'' challenges in mastering [si] and [?i]. In the first experiment, 93 monolingual Japanese speakers pronounced [si] and [?i] in the Japanese contexts, and listened to [si] and [?i] recorded by a native speaker of English. The participants all distinguished [si] and [?i] in both perception and production. Based on these results, I hypothesized that the [s] and [?] confusion by Japanese ESL learners is caused by misunderstanding. In the second experiment, 27 Japanese ESL students were recorded reading an English passage. After the reading the participants were taught the basic symbol-sound correspondence rules such as "s"-/s/ and "sh"- /?/. No articulation explanations were given. After the lesson, the participants read the same passage, and they pronounced /s/ and /?/ significantly more correctly. I concluded that the /s/ and /?/ confusion can be solved by teaching the English phonics rules without teaching the articulation.