Newly observed instances of reverse migration, i.e., migration from urban to rural areas, suggest that the labor market could be unstable. Using a Harris-Todaro-Lewis model, the authors provide a nonlinear bifurcation analysis that shows how unstable adjustments a nd chaotic fluctuations are possible and how these possibilities are related to adjustment speed, productivity, the relative importance of industry, and population size. Examples are given for hypothetical l ess-developed and developed countries using "plausible" parameter v alues. Coauthors are Sudipto Dasgupta, Samar K. Datta, and Jeffrey B. Nugent. Copyright 1987 by Royal Economic Society.