One measure of market efficiency is the speed at which prices adjust to fundamental value with the arrival of information. This paper examines this issue by estimating speed of adjustment coefficients using three methodologies for eight currencies for the entire year of 1996 using half hourly non-overlapping return intervals. We find that the bulk of adjustment to fundamental value for all currencies occurs within the hour but then quickly deteriorates. Within the hour adjustment is sufficiently quick to be considered efficient but the lack of full adjustment to fundamental value is not what would be predicted within an efficient market. There is no evidence for any of the currencies studied of a tendency to over react. There is also little difference in the speeds of adjustment between actively and less actively traded currencies. There is however a definite difference in the speed at which currencies adjustment depending on whether they are free floating or managed exchange rates. Free floating rates adjust much quicker. Government intervention slows adjustment to fundamental value.