Using the optical data of the 1993 international watch of NGC 5141, we made
follow-up reverberation mapping analyses of its broad line region (BLR). W
e found the transfer function of the BLR for the 1993 data is entirely diff
erent from that for the 1988 international watch. We conclude that the stru
cture of the BLR had changed in those 5 years and it is this change in stru
cture that is responsible for the very different sizes of the BLR deduced f
rom the two sets of data.