Air samples collected at Cape Grim, Tasmania (41 ¿S) between 1978 and 1995, and at Mace Head, Ireland (53 ¿N) between July 1994 and May 1995, have been analyzed by GC-MS to determine recent trends of HFC-134a, an important CFC replacement, in the background atmosphere. Until 1990, the concentration of HFC-134a at Cape Grim was below detection limits, the first quantifiable level (0.01 pptv) appearing in May 1990. Between 1992 and mid-1995 the concentration grew exponentially at ~200% yr-1, with the concentration at the end of 1994 reaching 0.43 pptv. At Mace Head, HFC-134a grew at a rate of 1.24¿0.11 pptv yr-1 between July 1994 and May 1995, with the concentration at the end of 1994 being 1.48 pptv. In the absence of industrial production and release estimates for HFC-134a, the observations have been used in conjunction with a 2-D global model to estimate recent emissions. The model indicates that significant emissions (250 tonnes) began in 1991, increasing rapidly to a level of ~8 ktonnes in 1994. ¿ American Geophysical Union 1996