Site 999 is located on a small rise in the Colombian Basin that was named the Kogi Rise during Leg 165. The Kogi Rise, ~150 km northeast of Mono Rise, lies nearly 1000 m above the turbidite-filled Colombian Basin (Fig. 1). Before drilling, the Planning Committee of the Ocean Drilling Program designated this site as a "legacy site" because of its strategic location for basement penetration into the still unsampled, westernmost portion of the Caribbean Oceanic Plateau. Site 999 is a reentry site, fully cased to 526.2 meters below seafloor (mbsf). Leg 165 objectives included reaching basement at Site 999; however, coring terminated at 1066.4 mbsf, 16 m below the Cretaceous/Tertiary boundary and at an undetermined level above volcanic basement. Significant (>150 m) basement penetration will be the primary objective when Site 999 is revisited during future drilling legs in the Caribbean (e.g., Duncan et al., 1999). The purpose of this data report is to establish total depth and two-way traveltime (TWT) at Site 999 and then provide an estimate for the depth and TWT to volcanic basement using velocity, depth, and TWT information derived from synthetic seismograms and physical properties data obtained during Leg 165 and multichannel seismic (MCS) velocity analyses. Re-evaluation of correlations between seismic stratigraphy and lithostratigraphy in light of log-generated synthetic seismograms and regional interpretations of seismic stratigraphy based on these correlations are beyond the scope of this data report.