A study examined the effects of using a musical clocklight as discriminative stimulus, paired with individual and group contingency rewards, on the decibel level in an elementary school lunchroom. Subjects were 256 students aged 5-12, who ate lunch in two sessions for younger and older students. The musical clocklight (MCL) apparatus consisted of a sound level meter that monitored and displayed decibels, a stoplight such as those used for traffic signals, a clock, a microphone, and a CD player. During the baseline condition, decibel levels in the lunchroom were measured at 30-second intervals. On the day prior to the initial MCL session, students were informed that the stoplight would change in accordance with noise levels and would control the delivery of music and the accumulation of time on the clock. If the noise became too loud, the light would turn red, the music would stop, and no time would accumulate on the clock. Upon accumulating 20 minutes per day for 12 days, the students would be awarded a pizza party. In addition, age-appropriate individual rewards were presented to students displaying appropriate behavior. Data indicate that the clocklight paired with reward contingencies decreased decibel levels significantly for both older and younger groups. The younger students reverted to baseline conditions when the clocklight was withdrawn. (SV)