Abstract: The distribution of various ⁵⁷Go-labelled Zhengguangmycin preparations, namely: single natural components A₂, A₄, A₅, A₆, B₂, a mixed preparation comprising of components A₂+B₂, and a single component derivation A₅₀₃₃ was studied in mice bearing solid type Ehrlich carcinoma. It was found that all these preparations exhibited antitumor and tumortropic properties. Among all the preparations, components A₅ and A₆ exhibited the strongest tumor-tropic property.Given at equivalent toxicity dosage (1/20 LD₅₀, components A₅ and A₄ exhibited the highest rate of tumor inhibition. The uptake of radioactivity in the mouse liver, kidney and tumor was the highest with component A₆ and the lowest with preparation A₅₀₃₃. It appears that A₆ would be the least promising component for clinical trial. The preparation A₅₀₃₃, beside the above mentioned properties, has the additional advantage of having a low uptake in the lung, rapid excretion through the kidney and the lowest acute toxicity. Moreover, A₅₀₃₃ exhibited a satisfactory tumor inhibition rate as compared with other prepations when given at equivalent toxicity dosage. It therefore appears to be worthy of further investigation from the point of diminishing pulmonary fibrosis. Though the uptake of component As in the mouse kidney and liver was rather high, yet it was lower than that of A₆. It was excreted slowly through the urine. On the ground that As has the strongest tumor inhibitory activity and a better retention in the animal body, it would also appear to be a component worthy of further study as an antitumor agent.