It has been very common to see collapse of structures, slopes, and foundations due to flow ofrnfoundation soils without observing any structural failure during earthquake. This can alsornoccur frequently and cause severe damages in this country following the occurrence ofrnearthquake, particularly in the Rift Valley region where there is a considerable deposit ofrnsaturated sand and silty sand. This problem has been studied in various countries andrnattributed to Liquefaction Phenomenon. The phenomenon occurs in saturated sand, whichrneither completely loses its strength and flow as a liquid (Flow Liquefaction, F.L) or shows arnprogressive softening (Cyclic Mobility, C.M.) under cyclic loading. Since liquefaction ofrnsand is entirely related to its undrained behavior, the undrained behavior of saturated sandrnunder cyclic or equivalent monotonic loading has been studied in the laboratory by differentrnresearchers, simulating field conditions properly for the better understanding of liquefactionrnphenomenon. The undrained behavior of saturated sand is useful to predict the occurrence ofrnthe probable type of liquefaction (C.M. or F.L) and to provide suitable solutions forrnliquefaction problem.rnThe objective of this research is therefore to study the undrained behavior of saturated sandrnin relation to liquefaction phenomenon based on intensive literature survey. This is bestrnexplained by identifying factors affecting the behavior and studying their effects observingrnthe resulting stress-strain and p-q diagrams. The concept of Liquefaction and steady staternare then discussed based on the undrained behavior of sand. Finally, the application of SteadyrnState Line (SSL) on the assessment of liquefaction potential and in the identification ofrnpartial liquefaction, limited liquefaction, and complete liquefaction is discussed.