This study was funded in part by a Minigrant award from California State University, Fresno. The use of thermal modalities to enhance stretching procedures is not well documented clinically. This study documented the effectiveness of applying superficial heat and cold in conjunction with a low-load prolonged stretch (LLPS) for increasing shoulder flexibility. Ninety-two healthy males were randomly assigned to one of five groups: 1) an LLPS alone, 2) heat applied in the initial phase of an LLPS, 3) cold applied in the final phase of stretch, 4) a combination of heat initially followed by cold, and 5) no intervention. Subjects received three, 40-minute treatments across a 5-day period. A follow-up measurement was taken 3 days later. Results demonstrated that an LLPS associated with the use of heat, ice, or a combination of both facilitated greater long-term improvements in flexibility compared with controls. However, only subjects receiving heat in the initial phase of an LLPS showed significant gains when compared with those who received stretching alone (p </= 0.05). We concluded that applying heat in conjunction with an LLPS to a nonpathologic shoulder is a clinically superior method of improving flexibility compared with an LLPS alone. J Orthop Sports Phys Ther 1992;16(5):200-207.