Starting from a sequential decision of international migration under incomplete information (see (1)) a Markov process for the number of in- and out-migrants from country j to country o is modeled. The parameters of this process involve the degree of uncertainty of the migrants about the quality of life in the guest-country before migration and indices of their productivity in the j - and o-economy. Using time series of in- and outmigration from and to the main countries sending guest-workers to the FRG these parameters will be estimated. In the paper the model of the mentioned Markov process is presented, thereby stressing the underlying microeconomic model, and some results of the econometric estimation of the parameters of the model. Finally some hints for the economic implications of the empirical findings will be given.