The use of the Delplot analysis to interpret the experimental results from the parallel-series reaction network A -> (k1) B -> (k3) C; A -> (k2) D under the influence of reaction reversibility was examined. A reactor model was used to test two experimental feeds, one with zero product species concentrations and the other with non-zero product species concentrations. The equilibrium constants K-1, K-2, and K-3 were varied between 0.2 and 1.5 for each reaction in the network. When C-A0 = 2.0 M and C-B0 = C-c0 = C-D0 = 0 M, it was found that reversibility did not change the analysis provided by the first-rank Delplots; i.e., species "B" and "D" are primary, while species "C" is non-primary. When C-A0 = 2.0 M and C-B0 = C-C0 = C-D0 = 0.5 M, it was found that the effect of the reversibility altered the information provided by Delplot analysis. For instance, the first-rank Delplot classified species "B" as a primary product when K-1 >= 0.5 but non-primary when K-1 = 0.2. A similar conclusion was also obtained for species D; i.e., species "D" was a primary product when K-2 >= 0.5 but non-primary when K-2 = 0.2. For species "C", it was found that species "C" is primary at high K-3 but non-primary at low K-3. In summary, when the feed has non-zero product concentrations and the reaction network contains reversible reactions, the species ranks suggested by standard Delplot analysis can be disguised. This would suggest that extra care should be practiced when Delplot analysis is used for reaction networks in which high reversibility may exist.