For linkage analysis projects aimed at mapping hereditary disease genes in humans, hundreds of highly polymorphic microsatellite markers which can be typed by PCR (PCR markers) have become available. With this technical improvement, the availability of a technique allowing for transparency in the handling of rapidly generated lod score data is becoming important. We present a computer program LODVIEW for the graphical representation of lod score data. It is designed for the input of lod score data generated with the LINKAGE package or similar programs. LODVIEW consists of 24 preformatted files, one for each chromosome. Each file contains a table for the input of lod score data and a file for the graphical representation of the data, which will show automatically any entry that is made in the respective input table. The program provides the user with published PCR marker information pre-entered into a table and graph at the correct positions corresponding to the genetic distances between markers. The graphical display of LODVIEW allows for the rapid evaluation of lod score results calculated from PCR markers on each chromosome. The following information can be obtained from the graphical display at one glance: (i) Regions of exclusion (Z(theta) < -2) and nonexclusion, (ii) markers with positive lod scores, (iii) the distribution of positive and negative lod scores among the families examined (indication of genetic heterogeneity), (iv) multipoint lod scores, and (v) the availability of PCR markers in regions of interest. The program is continually updated for novel PCR marker information from the literature. The program will help to efficiently monitor and direct the progress of exclusion mapping projects.