Enhanced bioremediation of acetylene is persistent long-term, and inducible in multiple genera of microorganisms. A 1985 field denitrification study failed due to enhanced biodegradation of acetylene that resulted from acetylene additions to the soil four years earlier. Rhodococcus spp. was found to use C2H2 as its sole carbon source and thrive on the gas. After 25 years without exposure to the gas it was hypothesized that Rhodococcus spp. would still be able to utilize C2H2. This study sampled the same area studied in past studies and identified the acetylene decomposers. The location of the acetylene decomposers matched the location of C2H2 exposures in 1981 and in 1984. This study we report that enhanced acetylene biodegradation persists in soils exposed to the gas as long as 25 years in the past. Bacteria capable of using C2H2 as sole carbon source were isolated and identified by MIDI analysis as: Rhodococcus rhodochrous, Rhodococcus wratislaviensis (Tsukamurella), R. erythropolis/R. globerulus/N. globerulam, and Arthrobacter oxydans.