Isotopes of astatine lighter than mass 205 were studied at the Heavy Ion Linear Accelerator by bombardment of 185Re and 187Re with 20Ne, using Si (Au) surface barrier detectors in on-line measurements. Mass number assignments of astatine 201 through 196 are based on excitation functions and on genetic relationships with polonium isotopes. Accurate alpha energies are reported for 204At through 196At, for 202Po through 194Po and for four light bismuth isotopes. Half-lives are given for 202At through 196At, and for the bismuth isotopes. Isomerism was detected in 202At, 200At and 198At.