The following study aims to examine the infant mortality in Kronoberg county in southern Sweden during four intervals 1820–1840, 1860–1880, 1900–1920 and 1930–1949, and thereby during the three latter stages of the demographic transition. The empirical data has been obtained from the region's central town, Växjö, and 16 different parishes on the countryside. As stated, the main issue is to study the development of infant mortality, but also to investigate whether there was any regional variation and whether the mortality was higher among the illegitimate children. The results show that infant mortality decreased from 173 to 35 per mille and that the urban parts of the study area initially had the highest mortality, but until the last interval it was lo­west in the urban environment. The highest infant mortality rate was observed among those born out of wedlock, which also declined from 262 to 65 per thousand throughout the studied periods.