DNA STR profiles have been generated from 1 ng and low copy number (LCN) templates using 28 and 34 cycles of amplification, respectively. Characteristics which facilitate the interpretation of profiles, such as heterozygous balance, allelic dropout and stutter proportions have been quantified. We demonstrate that a reduction in DNA template coupled with an increase in amplification cycle number produces an increased rate of allelic dropout out which can be correlated to the peak areas of those alleles observed. In addition, the LCN conditions increase the degree of peak area asymmetry observed from heterozygotes and the size range of stutters. Analysis of the data allows us to develop sets of guidelines appropriate for interpreting both single and mixed DNA profiles.