The aim of this paper is to evaluate the impact of different factors such as age, gender, ethnicity, education levels, occupations, enterprise characteristics, place of residence etc. on part-time employment and underemployment. The data sources used in the research are Latvian Labour Force sample surveys conducted in May 1999 and May 2000. Methodology includes exploratory data analysis and binomial logit models. The main findings are as follows: age is a significant factor, which influences both part-time employment and underemployment; however, the effects are of opposite directions. Women are more likely to work part-time. The underemployment level is higher for individuals with a basic education and lower for those with a higher education; however, there is no clear-cut relationship between education and working part-time. Working in the public sector decreases the probability of being employed part-time and of being underemployed. Inhabitants of rural areas are more likely to be employed part-time and underemployed, as compared to those of urban areas; on the other hand, there is no significant difference between Latvia’s regions in these two respects.