Quantitative structure–activity relationship (QSAR) of tetrabutyl­phosphonium bromide (TBPB) analogs as muscarinic acetylcholine receptors (mAChRs) agonists was studied. A suitable set of molecular descriptors was calculated and stepwise multiple linear regression (SW-MLR) was employed to select those descriptors that resulted in the best fitted models. A MLR model with three selected descriptors was obtained. Furthermore, the MLR model was va­lidated using the leave-one-out (LOO) and leave-group-out (LGO) cross-vali­dation, and the Y-randomization test. This model, with high statistical signifi­cance (R2train = 0.982, F = 388.715, Q2LOO = 0.973, Q2LGO = 0.977 and R2test = 0.986) could predict the activity of the molecules with a percentage predic­tion error lower than 5 %.