[amelia] impossible values

I'm imputing values for missing blood lipids (roughly 20% out of 3000 observations) in a cross-sectional data set. Some of the imputed values are not possible (for example, negative triglycerides levels). I'm not sure how to handle these imputed values. Should I just ignore then and go ahead with the analysis? Is it possible to impose restrictions on the model (using Amelia) to make all triglyceride values positive? Any suggestions will be appreciated. Leonelo E. Bautista, MD, DrPH Assistant Professor University of Wisconsin Medical School Population Health Sciences 610 Walnut Street, 703 WARF Madison, WI 53726-2397 Phone: (608)265-6176 Fax: (608)263-2820