Thiourea, when present at low concentration, can act as a radiation protector to macromolecules (biological or polymeric) in aqueous solution. Previous work has shown that much of this protection occurs against the indirect effect. Thiourea can also protect against the direct effect, though to a more limited extent. In this paper the reactions of dilute aqueous thiourea solutions have been followed at a range of $\gamma$ radiation doses and dose rates, and in the absence and presence of oxygen. The rapid destruction of thiourea confirms that the effect is primarily indirect, and almost independent of concentration, and dose rate over the range 10 to 500 mg/l. The breakdown products of thiourea can react further. In the presence of oxygen the loss of thiourea is more rapid, and different products are formed.