According to bilateral agreement signed by the Polish and German governments in 1990, Polish workers are allowed to take up seasonal employment (short term and legal) in specific sectors of German economy. In the last couple of years, this relatively new form of migration constitutes a significant part of Poles' labour mobility. The author presents a general overview of the socio-economical aspects of seasonal migration with a special emphasis on reasons of the successful implementation of the 1990 bilateral agreement. Using unique quantitative data from national representative survey of the Polish seasonal workers an attempt was made to explain scale and patterns of this kind of mobility in the context of contemporary migration from Poland.