Are you referring to a Ginseng Ficus by any chance? If so, it is not uncommon for Ficus to drop their leaves when their environment changes. A move to a new location can trigger this. Have you moved it recently or perhaps just acquired it. Has it been subjected to a period with insufficient water? Have you recently fertilized it and if so in what concentration? You have not really given us much to go on, more information may help. Pictures certainly would not hurt either.
I am having hte same problem. I bought my plant from a reputable Bonsai gardener almost 2 yrs ago. The first year everything went fine, but this year the leaves are shriveling up and falling off. There are new leaves beginning to bud at the tip of each branch. I think that I neglected it while I was sick. Besides watering it, what else can I do. Because new leaves have budded, does that mean I still have a chance to save it? It is a 10 yr old beautiful plant...I am sick that I may lose it.