This thesis examines the behavior of prices following the unexpected arrival of a large number of immigrants from Syria to Lebanon between 2012 and 2014. Using Lachs model with monthly data about prices, number of immigrants and natives, the total effect of immigration on lebanese prices was estimated. The final estimation that a one-percentage-point increase in the ratio of immigrants to natives decreases prices in Lebanon by 0,21 percentage-point, is consistent with introduced hypothesis and theory. It is argued that the reason for decrease are mainly lower immigrants wages which derive from their lower qualification.