SummarySince 1974 an intensive investigation of the occurrence of low-level jet (LLJ) is conducted in tl~e Bavarian pre-alpine region and in the mountain valleys around Garmisch-Partenkirchen. Until now about 1500 balloon flights, usually tracked by double-theodolite observation, have been evaluated. The observed cases of LLJ have been divided into 4 types. Type (a) orographic LLJ; this type is observed during FOhn, Bora, or other local wind conditions. Type (b) -thermal LLJ; valley and mountain wind, for instance, belong to this type. Type (c) nocturnal LLJ; this type mainly forms during evening, night, or morning hours, and its development is caused by the reduction of the turbulent vertical exchange. Type (d) -LLJ of synoptic scale; this type is observed during pre-frontal conditions and is caused by the approach of a front. Highest wind speeds have been observed with types