Four new potential MR imaging contrast agents were synthesised. Gadolinium-hematoporphyrin (Gd-H) was produced by inserting gadolinium into the naturally occurring porphyrin,hematoporphyrin.Gadolinium-tetra-carboranylmethoxyphenyl-porphyrin acetate (Gd-TCP)was similarly synthesised by gadolinium insertion into the synthetic porphyrin, 1, 6, 11, 16-tetra-[3-(carboranylmethoxy)phenyl] porphyrin. The monoclonal antibodies, 9.2.27 against melanoma and WM53 against leukaemia cell lines, were conjugated with cyclic anhydride gadolinium-diethylenetriaminepenta-acetic acid (Gd-cDTPAa), yielding the attachment of chelate DTPA to the antibodies. Gadolinium ion was inserted into the chelate DTPA, thus labelled both these antibodies with Gd-DTPA. Overall, with the satisfactory low levels of gadolinium in the liver, kidneys, and spleen, and good tumour uptake, gadolinium antibody conjugates has considerable potential for further diagnostic applications of MR imaging. / Doctor of Philosophy (PhD)