We have developed an Internet translation service, which we began to provide in 1997 for English to Japanese translation and in 1998 for Japanese to English. In this service, users send a translation request from a web page and receive by e-mail the result of the translation outputted by Toshiba’s machine translation system. As in other similar services, users can specify English-Japanese word pairs(dictionary data) when making a translation request. What distinguishes our service from others is that our service system constructs users’ own dictionaries on the server and helps them with this work by extracting words which the system expects to improve the system's translation quality if included in the dictionaries. With this function, users can efficiently add new word pairs so as to upgrade their own dictionaries when requesting re-translation. The dictionary data thus obtained from users can be utilized to improve the system dictionary on the server also.