The present invention encompasses the finding that improvements can be achieved in manufacture of isocyanates through the use of a substitute for or a precursor of phosgene. Methods and compositions utilized in accordance with the present invention can be useful in situations in which it is difficult to use phosgene, and in particular gaseous phosgene. In some embodiments, a substitute for or a precursor of phosgene used in accordance with the present invention for preparing isocyanates is or comprises diphosgene (ClCO2CCl3).