We present a simulation study of the TCP performance in ATM networks with available bit rate (ABR) service and unspecified bit rate (UBR) service with early packet discard (EPD) schemes. We focus our study in a LAN environment using some benchmark network configurations proposed in the ATM Forum. Our simulation results show the following: (1) with UBR service and EPD schemes, TCP suffers significant performance degradation in terms of fairness and requires relatively large switch buffer even with a small number of active virtual connections over a LAN configuration, and (2) for the same set of network configurations and with ABR service using explicit rate feedback schemes, TCP achieves a good performance in terms of fairness and link utilization, and requires a relatively small switch buffer.