Amine and urea analogs of ferrochloroquine with varying methylene spacer lengths were synthesised, studied by cyclic voltammetry and evaluated in vitro against a sensitive (D10) and resistant (K1) strain of Plasmodium falciparum. Most analogs were found to be more active than chloroquine in both strains. In D10 ureas were more active than amines and antimalarial activity in this strain correlated well with the length of the methylene spacer and redox potentials. The length of the methylene spacer was a major determinant of antimalarial activity in K1.