The purpose of the work was to study the synthesis of the pyrrolo[2,1-α]phthalazine system, and of the related systems, and routes to substituted derivatives with a view to producing compounds of potential antihypertensive activity. The effect of substitution particularly at and in the region of the 6-position of pyrrolo[2,1-α]phthalazine, was of interest, by analogy with the substituted phthalazine antihypertensive agent, hydralazine.