  The discovery of hard X-ray sources near the top of a flaring loop by the HXT
instrument on board the YOHKOH satellite represents a significant progress
towards the understanding of the basic processes driving solar flares. In this
paper we extend the previous study of limb flares by Masuda (1994) by including
all YOHKOH observations up through August 1998. We report that from October
1991 to August 1998, YOHKOH observed 20 X-ray bright limb flares (where we use
the same selection criteria as Masuda), of which we have sufficient data to
analyze 18 events, including 8 previously unanalyzed flares. Of these 18
events, 15 show detectable impulsive looptop emission. Considering that the
finite dynamic range (about a decade) of the detection introduces a strong bias
against observing comparatively weak looptop sources, we conclude that looptop
emission is a common feature of all flares. We summarize the observations of
the footpoint to looptop flux ratio and the spectral indices. We present light
curves and images of all the important newly analyzed limb flares. Whenever
possible we present results for individual pulses in multipeak flares and for
different loops for multiloop flares. We then discuss the statistics of the
fluxes and spectral indices of the looptop and footpoint sources taking into
account observational selection biases. The importance of these observations
(and those expected from the scheduled HESSI satellite with its superior
angular spectral and temporal resolution) in constraining acceleration models
and parameters is discussed briefly.
