Previously, an "additivity" equation relating experimental 13 C chemical shift data for two monosubstituted diphenyl-1,3-thiazolidin-4-one series was developed to predict chemical shifts for a similarly substituted bis-disubstituted thiazolidinone series. The sites of interest in the 1,3-thiazolidin-4-one are at the C-2, C-4, and C-5 carbons. The empirically derived equation for predicting the chemical shifts iswhere  XY is the predicted chemical shift for the disubstituted thiazolidinone,  H is the experimental chemical shift for the unsubstituted thiazolidinone,  X is the experimental chemical shift for substituent in the 2-phenyl ring, and  Y is the experimental chemical shift for substituent in the N-(3)-phenyl ring. This article discusses the application of the aforementioned equation with respect to a new series of 2-(p-chlorophenyl)-substituted-3-phenyl-1,3-thiazolidin-4-oneswith a comparison of both experimental and predicted 13 C chemical shifts for the C-2, C4 and C-5 sites in the thiazolidinone ring. Utilization of the equation showed a level of chemical shift predictability with a degree of accuracy in concert with a previously reported series. The degree of predictability again showed a dependency on the particular substituent and the chemical shift for the site being predicted. This was ±0.06 ppm for C-2, ±0.2 ppm for C-4 and ±0.09 ppm for C5. Finally, there was a correlation between Hammett  values and the substituent chemical shifts using13 C values at C-2. The r value was -0.86 indicating that the C-2 carbon preferred a positive charge.