An　analysis　of　an　asynchronous　DS-BPSK　UWB　system　is　presented.　The　standard　UWB　channel　(proposed　by　IEEE　802.15.3a　task　group)　rather　than　AWGN　or　any　other　kinds　of　multipath　fading　channels　[1]-[4]　is　employed　in　the　analysis　to　reflect　the　actual　channel　conditions.　We　adopt　the　standard　Gaussian　approximation　in　the　analysis　because　of　its　facilities　in　analyzing　the　complicated　multipath　fading　channel　which　comprises　many　random　variables.　The　result　of　this　analysis　reveals　that　in　certain　channel　conditions,　the　bit　error　probability　of　such　systems　is　influenced　by　several　key　parameters　which　include　the　period　of　the　pseudo-random　code,　the　mean　of　the　squared　value　of　the　pulse＇s　normalized　autocorrelation　function,　and　the　expected　sum　of　the　squared　value　of　discrete　aperiodic　cross-correlation　function　between　every　two　different　signature　sequences.　The　impacts　of　the　above　key　parameters　are　revealed　by　both　analysis　and　numerical　examples.　©　2006　IEEE.