Abstract The ammonical silver banding technique has been used to stain the polytene chromosomes of Rhynchosciara hollaenderi. The initial regions to stain black with this technique are regions which hybridize with rRNA. The pattern of silver staining in the NOR of the X-chromosome corresponds closely with the regional clumping of grains observed after in situ hybridization with rRNA. This region of the X-chromosome is much more active than any other rRNA hybridizing region in the formation of nucleoli and is also Ag-banded more frequently. This implies that regions most active in rRNA production may preferentially Ag-band. The use of this technique to study the production of nucleoli and micronucleoli in sciarid polytene chromosomes is discussed as are the potential contributions of these chromosomes to arriving at a better understanding of the mechanisms of silver banding.