What determines exporters" exchange rate hedging decisions and do exporters attempt to "time the market"? We use a unique unit record longitudinal administrative dataset on firm exports to find the determinants of exporters" currency hedging choices. Determinants include financial fragility, prior hedging experience, and natural hedge opportunities. In addition, firms alter their hedging ratios when the currency has recently trended in one direction. We test whether such behaviour reflects firm characteristics (such as pricing power). We find that these responses are ubiquitous for all but large firms and for all times other than when the exchange rate is near its extreme high or low historical values. These results are consistent with most firms practicing selective hedging (market timing) behaviour that reflects a belief in exchange rate momentum effects. However, this behaviour appears sub-optimal since momentum effects are statistically absent from the underlying exchange rate data.