We interpret a MACCS-FP-SVM toxicity classifier by inspecting the vector w ∈ R 166 normal to its separating hyperplane. Weight w i ∈ R in w is associated with MACCS keybit i , which looks for a particular subgraph pattern in the molecular graph. For ease of interpretability, here we do not standardize the input MACCS FPs and instead retain them as bit vectors; consequently, a positive (negative) coefficient w i implies the presence of the subgraph pattern described by MACCS keybit i tends to produce a prediction of toxicity (non-toxicity).