Food-service establishments that use on-site wastewater treatment systems are experiencing pretreatment system and/or drain field hydraulic and/or organic overloading. This study included characterization of four wastewater parameters (five-day biochemical oxygen demand [BOD5]; total suspended solids [TSS]; food, oil, and grease [FOG]; and flow) from 28 restaurants located in Texas during June, July, and August 2002. The field sampling methodology included taking a grab sample from each restaurant for 6 consecutive days at approximately the same time each day, followed by a 2-week break, and then sampling again for another 6 consecutive days, for a total of 12 samples per restaurant and 336 total observations. The analysis indicates higher organic (BOD5) and hydraulic values for restaurants than those typically found in the literature. The design values for this study for BOD5, TSS, FOG, and flow were 1523, 664, and 197 mg/L, and 96 L/day-seat respectively, which captured over 80% of the data collected.