Apl, a gene involved in the processing of lysosomal acid phosphatase in mouse liver, has been mapped on Chromosome 17. The gene order and map distances in per cent recombination of the loci studied are T (20.6 +/- 3.4) Pgk-2 (7.4 +/- 2.2) Apl. Thus, Apl is at least 7 cM distal to H-2 on this chromosome. In addition, strain-specific allelic variants for Apl have been demonstrated on cellulose acetate gels, a quick and inexpensive method of electrophoresis.