"Fox on the Run" became Sweet's third Top Ten hit as the second single from Desolation Boulevard, their most successful release. The song reached the number five spot in the U.S. and number two in the U.K., becoming the band's second million-selling single (after 1973's "Little Willy"). Desolation Boulevard marked a noticeable transition within the band, as they were attempting to adopt a slightly harder rock format which was fully accomplished on 1978's Level Headed album. The band wrote "Fox on the Run" themselves, initiating a blatant bid to shed themselves of Nicky Chinn and Mike Chapman's bubblegum songwriting recipe, which had been a staple of Sweet since the early '70s. Even though "Fox on the Run" combined a heavy guitar crunch with Brian Connolly's high-pitched but rock-groovy vocals, it still harbored a slight glam rock sound in its flashiness. This mixture of their old and new style is what makes "Fox on the Run" so effective as both a pop and rock song. While there's no mistaking the colorful gloss that's initiated by the echo effect of the vocals, it's counterattacked just as quickly by the raw guitar and percussion work throughout the rest of the song. It may not be of the hardest caliber, but it proved that Sweet was headed toward a more serious (and musically nutritious) sound. Other songs from the album, like "Sweet FA" and "Set Me Free," instilled the same characteristics, but "Fox on the Run"'s slick '70s flow and catchy rhythm make it one of the group's most pleasing songs.