Continuous and non-invasive blood pressure (BP) measurement systems generally utilize applanation tonometry. Besides their relatively higher cost compared to conventional cuff-based systems, these are not yet practical during movement of the subject. This may explain their application to clinical researches instead of operation rooms. Another approach is based on measurement of the pulse transit time (PTT). Although the precision and accuracy of the presented models are reported to be acceptable in the literature, devices purely based on PTT have not yet been released commercially. One of the most important reasons is that these methods need calibration at regular intervals. In this paper a number of PTT-based methods have been reviewed. Two definitions of the PTT related to the systolic and diastolic pressures are presented, based on the current literature. The accuracy of these models was evaluated using their correlation coefficient of systolic and diastolic BP with these PTT. Results show that Fung's algorithm can estimate BP more accurately than other algorithm based on its correlation coefficient of 94.8% for systolic and 92.46% for the diastolic BP respectively.