The general workflow goes like this: Read the shapefile into ENVI (which makes a new EVF format vector file out of it), then write the vectors out to DXF. Here are where you find the tools to do it: 1. From the main ENVI menu choose Vector > Open Vector File. Here you will want to change the file selection filter to *.shp (by default it's *.evf, looking for ENVI format vector files only). Select your shapefile, then click Open. 2. From the main ENVI menu, choose Vector > convert EVF to DXF, then select the EVF file you just made while importing the shapefile. I hope that helps.