This paper investigates the secure transmission of information over an ergodic fading channel in the presence of an eavesdropper, similar to Wyner's wiretap channel. The authors characterize the secrecy capacity under two scenarios: full Channel State Information (CSI) at the transmitter, where both the legitimate receiver and the eavesdropper's CSI are known, and only the legitimate receiver's CSI is known. For the full CSI case, an optimal power allocation strategy that achieves the secrecy capacity is derived. For the scenario with only the legitimate receiver's CSI, a variable rate transmission scheme is proposed, which is shown to approach the optimal performance as the average signal-to-noise ratio (SNR) increases. The paper also introduces an on/off power allocation scheme that achieves near-optimal performance with only the main channel CSI, and it is shown that this scheme attains the secrecy capacity under the full CSI assumption. The results highlight the positive impact of fading on secrecy capacity and the critical role of rate adaptation based on the main channel CSI in facilitating secure communications over slow fading channels.This paper investigates the secure transmission of information over an ergodic fading channel in the presence of an eavesdropper, similar to Wyner's wiretap channel. The authors characterize the secrecy capacity under two scenarios: full Channel State Information (CSI) at the transmitter, where both the legitimate receiver and the eavesdropper's CSI are known, and only the legitimate receiver's CSI is known. For the full CSI case, an optimal power allocation strategy that achieves the secrecy capacity is derived. For the scenario with only the legitimate receiver's CSI, a variable rate transmission scheme is proposed, which is shown to approach the optimal performance as the average signal-to-noise ratio (SNR) increases. The paper also introduces an on/off power allocation scheme that achieves near-optimal performance with only the main channel CSI, and it is shown that this scheme attains the secrecy capacity under the full CSI assumption. The results highlight the positive impact of fading on secrecy capacity and the critical role of rate adaptation based on the main channel CSI in facilitating secure communications over slow fading channels.