The VIIRS Land Surface Temperature (LST) algorithm represents a significant departure in the conventional approaches that have been employed for retrieval of LST. As with the VIIRS Sea Surface Temperature algorithm, the LST algorithm utilizes a dual split-window approach, with both Short-wave Infrared (SWIR) channels at 3.70 µm (M12) and 4.05 µm (M13), and Long-wave Infrared (LWIR) channels at 10.76 µm (M15) and 12.01 µm (M16) to correct for atmospheric water vapor. Previous LST algorithms only used the LWIR bands in the retrieval of surface temperature because of the concern for both solar contamination and large emissivity variations in the SWIR bands. In this presentation, we assess whether these concerns are real and whether there is an impact on the precision and accuracy of the LST retrieval. We have taken two separate approaches to perform this testing, one based solely on global synthetic data and the other based entirely on proxy data from Tera MODIS. Results of both the split-window and dual split-window algorithms are assessed by either comparisons to synthetic "truth" or results of the MODIS retrieval. We also show that the results of the testing with proxy data are consistent with those obtained using the global synthetic data.