The low resolution of standard 2D HMBC spectra makes it very difficult to assign signals of close pairs of carbons. The NASCA-HMBC (Non-ambiguous Assignment by Superposition of Coupled Aliased HMBC) combines a pair of aliased HMBC spectra to provide one order of magnitude increase in the resolution. Application to agathisflavone, a biflavonoid found in Ouratea gilgiana resulted in spectra with a sufficiently high resolution to make the assignment straightforward and report, for the first time, its full assignment.