Delayed neutron yields and decay constants for 235U, 237Np, 241Am, and 243Am were measured at the Texas A&M University TRIG A reactor using a fast pneumatic transfer system. The detection system consisted of an array of BF3 proportional counters embedded in a polyethylene cylinder. The measured values of the total delayed neutron yield per 100 fissions from thermal neutron-induced fission of 235U, 237Np, 241Am, and 243Am were determined to be 1.59 ± 0.04, 1.29 ± 0.04, 0.49 ± 0.02, and 0.84 ± 0.04, respectively. The newly measured values of delayed neutron group parameters and total yields were compared with other values recommended by Keepin; Waldo, Karam, and Meyer; and Tuttle. Very good agreement was obtained, especially for 235U.