Divergent component of total water vapor transport has been calculated for January, February, and March of 1998 El Niņo and 1999 La Niņa periods, by introducing water vapor transport potential function and separating the water vapor transport into rotational and divergent components. We assumed horizontal divergence of water vapor (divQ) is balanced by the evaporation minus precipitation, i.e., divQ=[E-P]. SSM/I-derived precipitation and evaporation rate from SSM/I wind and total precipitable water, in conjunction with NCEP SST and surface air temperature, are used for the calculation of the transport potential function. Results indicate that there are distinct differences in water vapor transport between El Niņo and La Niņa periods. During the El Niņo period (January 1998), dominant vapor source regions are found in the oceans extending from the subtropical North Pacific to the East Pacific off the Peruvian coast. It is also noted that the vast area of Indian ocean and central to western portion of equatorial South Pacific served as moisture sink region. Combining the source and sink regions, the dominant water vapor transport took place in the north-south direction, however, it led to east-west coupled dipole-like pattern of anomalous transport. By contrast, an east-west coupled water vapor transport pattern, associated with the enhanced Walker circulation during the La Niņa period (January 1999), appeared in the tropical ocean. Anomaly map indicated that the tropical central Pacific served as an anomalous vapor source region.