When the PCF (Point Coordinated Function) MAC protocol is combined with the frame aggregation method to enhance the MAC performance in IEEE 802.11 wireless LANs, the formulae for the optimal frame aggregation level for best PCF MAC performance were derived in our previous study. We extend the formulae for the PCF protocol to derive the optimal frame aggregation level for the connectivity-based multipolling MAC protocol in IEEE 802.11 wireless LANs. By simulations, we compare the performances of IEEE 802.11 wireless LANs with the optimal and random frame aggregation levels. Compared with the random frame aggregation level, the optimal frame aggregation level significantly improves the performance of IEEE 802.11 wireless LANs.