Two drug combinations were tested during 18 field captures of 14 individual impala in northern Kenya in 1966–67. Nine additional impala, eight females and one male, were darted but not captured. Dosages of 0.45 mg M.99+10.0 mg acepromazine+4.5 mg hyoscine were adequate for males, but did not completely immobilize them. Females proved more difficult to capture, and all attempts using the acepromazine mixture were unsuccessful. The substitution of phencyclidine for acepromazine, and the deletion of hyoscine, proved a more suitable mixture. A dosage of 0.32 mg M.99+90 mg phencyclidine per animal completely immobilized both sexes. The phencyclidine-M.99 mixture was judged an improvement over other common field immobilizing drugs, but the long recovery time limits the usefulness of this drug combination for large-scale capturing operations.