VNA measurement stability is perennially an important topic since it affects how often one must calibrate, data reproducibility and, ultimately, the level of confidence in the measurements being performed. With true-mode stimulus measurements, the same types of questions apply. Since the measurement process is somewhat different, however, it may be useful to examine some of the dependencies and what performance can be achieved. This paper will examine how some stability mechanisms interact in the true-mode stimulus measurement class in the MS464XB and some typical measurement results.