Sampling is the backbone of marketing research. This chapter introduces the various probability and non-probability sampling designs as applicable to marketing research. Population is the entire aggregation of items from which samples can be drawn. Population is also called universe. It may be defined as any identifiable and well-specified group of individuals. In general, sample size depends on the nature of analysis to be performed, one wish to achieve the estimates of the desired precision, number of variables that have to be simultaneously examined, and spread of heterogeneous population. Sampling frame, at a stage of sampling process, is a list of all sampling units belonging to the population to be studied with their proper identification and available for selection. In cluster sampling, we divide the population into groups having heterogeneous characteristics called clusters and then select a sample of clusters using simple random sampling.