A number of the derivatives of dihydron aphthalono were prepared; their structures were established through chemical transformations (see flow sheet) and by their spectral data (fig.1, tables 1 and 2).The previous assignment of structure Ⅲ to their carbonation product by Walker and Scott^[2] is shown to be incorrect Pyrolyses of the various diesters Ⅵ are reported.The polymor of benz-p-quinodimothane (Ⅱ) was obtainod in small amounts.