The merged TOPEX/POSEIDON and ERS-1/2 altimeter data from 1993 through 2001 and the Spectral Element Ocean Model (SEOM) have been used to investigate Indian Ocean Kelvin waves (IOKWs), specifically their propagation and energy intrusion into Lombok Strait. The altimeter data show the frequent occurrence of IOKWs in either April/May or November/December for the years of 1993--2001 (except 1994) with intraseasonal wave periods (phase speeds) ranging from 35 (1.5) to 90 days (2.9 ms-1). From the altimeter data, it is estimated that 55.6 ¿ 13.9% of the incoming IOKW energy enters Lombok Strait. The SEOM results indicate an energy intrusion rate of 65%, showing good agreement with the altimeter data. The majority of the incoming IOKW energy is used to increase Kelvin wave energy entering Lombok Strait. This suggests that Lombok Strait acts as a significant transition point for Kelvin wave energy from the Indian Ocean to the internal Indonesian Seas.