Abstract. It is well-known that the low surface brightness (LSB) galaxies are gas-rich and yet have a very low star formation rate. The particular case of UGC 7321 will be discussed where high gas dispersion, as deduced from our dynamical study, is argued to be responsible for the low star formation rate. This article highlights some of the dynamical issues including the low star formation seen in the LSB galaxies, and points out the open problems in this topic.

Key words: galaxies: halos -- galaxies: individual -- UGC 7321 -- galaxies: kinematics and dynamics -- stars : formation