In the beginning of the 19th century, Swedish was the only official language of Finland, and thus the dominating language in administration and higher education. However, during the latter part of the century, efforts were made to develop Finnish into a language which could be used in every part of society. In 1881, the medical society Suomalainen Lääkäriseura Duodecim was founded with the development of a medical terminology in Finnish as one of its main purposes. In 1885, a medical paper, Duodecim, and a medical dictionary were published. The aim of this study is to illuminate the vocabulary of the dictionary.