Infant mortality is a major public health problem, especially for Lao PDR. Infant mortality rate in Lao PDR (67.2 per 1000 live births, Census 2005) is highest among ASEAN countries, except Cambodia. Thus, the purpose of this study is to identify factors affecting infant mortality in order to make more effective intervention program to reduce infant mortality. These factors include maternal, socio-economic and environmental factors. The study utilizes secondary data from Lao PDR, Multiple Indicator Cluster Survey, 2006. The units of analysis are women aged 15-49 years who gave births one year before the survey. Among 944 mothers included in the analysis, 7.7 percent experienced infant mortality. Binary logistic regression utilized for assessing the net effects of all independent variables on infant mortality. The results reveal that the relationship between maternal factors (age of mother, antenatal care, assistance at birth), socioeconomic factors (area of residence and household economic status) and infant mortality are statistically significant. Mothers aged 15-19 years have the highest infant mortality. Mothers who had no ANC, did not receive any assistance during delivery, live in rural area, in the poorest households are most likely to have infant mortality. Based on the findings, some policy implications are suggested.