The motion to amend the bill of particulars was properly denied where it was made on the eve of trial, 10 years after the alleged malpractice and 8 years after service of the original bill of particulars, and plaintiffs failed to offer an adequate explanation for such delay. Further, the proposed amendment propounds material changes, introducing new theories of malpractice inconsistent with those previously alleged, such that defendants would be severely prejudiced were the amendment allowed ( see, Spielberger v Giambalvo, 207 AD2d 877).