The parameters T_90_ and T_50_ have recently been introduced as a measurement of the duration of gamma-ray bursts. We present here a description of the method of measuring T_90_ and T_50_ and its application to gamma-ray bursts observed with the Burst and Transient Source Experiment (BATSE) onboard the Compton Gamma-Ray Observatory (CGRO). We use simulated as well as observed time profiles to address some of the possible systematic effects affecting individual T_90_ (T_50_) measurements. We show that these systematic effects do not mimic those effects that would result from time dilation if the burst sources are at distances of several Gpc. We discuss the impact of these systematic effects on the T_90_ (T_50_) distributions for the gamma-ray bursts observed with BATSE. We distinguish between various types of T_90_ (T_50_) distributions, and discuss the ways in which distributions observed with different experiments can vary, even though the measurements for commonly observed bursts may be the same. We then discuss the distributions observed with BATSE and compare them to those observed with other experiments.