A measurement is presented of the associated production of a single top quark and a Z boson. The study uses data from proton-proton collisions at, root s = 13 TeV recorded by the CMS experiment, corresponding to an integrated luminosity of 35.9 fb(-1). Using final states with three leptons (electrons or muons), the tZq production cross section is measured to be sigma (pp -> tZq -> Wbl(+)l(-)q) = 123(-31)(+33)(stat)(-23)(+29)(syst) fb, where l stands for electrons, muons, or tau leptons, with observed and expected significances of 3.7 and 3.1 standard deviations, respectively. C) 2018 The Author. Published by Elsevier B.V.