A multiple acess protocol, which can be used in a VSAT network, with an adaptive and hybrid assignment is considered. In this protocol the transmission can be done in either an S-Aloha channel or in a demand assignment TDMA channel. The remote stations have finite buffer capacity to store arriving messages. The performance is evaluated in terms of throughput and expected delay, by means of the so called Equilibrium Point Analysis (EPA). Stability of the protocol is also examined. A comparison between this protocol and an S-Aloha one, both with the same bandwidth, is also carried out. Variations of the basic protocol considering the demand assignment TDMA channel with a smaller bandwidth than that one of the S- Aloha channel are also considered. Another important variation examined is the one in which W S-Aloha channels serve W separate groups of remote stations and all share a demand assignment TDMA channel. For this variation, modification in the equilibrium equations obtained for the basic protocol as well as for expression of throughput and expected delay are indicated. Numerical results of throughput and expect delay for the several protocols are given.