The invention provides novel 7,8-dihydro-imidazo[1,2-.alpha.]pyrazolo[4,3-e]pyrimidin-4-onecompounds and 7,8,9-trihydro-[1H or 2H]-pyrimido [1,2-.alpha.]pyrazolo[4,3-e]pyrimidin-4(5H)-one compounds, substituted at the 1 or 2 position with C2-9alkyl,C3-9 cycloalkyl, heteroarylalkyl, or substituted arylalkyl, in free, salt orprodrugform, processes for their production, their use as pharmaceuticals,particularly asPDE1 inhibitors, and pharmaceutical compositions comprising them.
