Two pyridopyrrolopyrimidine alkaloids, variolin A (2) and N(3')-methyl tetrahydrovariolin B (3), have been isolated from the Antarctic sponge Kirkpatrickia varialosa, and their structures determined by X-ray crystallography and interpretation of spectral data respectively. N(3')-Methyl tetrahydrovariolin B (3) is moderately cytotoxic and showed antifungal activity, while variolin A (2) is weakly cytotoxic.