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We have measured the parity-violating electroweak asymmetry in the elastic scattering of polarized electrons from the proton. The kinematic point [͗u lab ͘ 12.3 ± and ͗Q 2 ͘ 0.48 ͑GeV͞c͒ 2 ] is chosen to provide sensitivity, at a level that is of theoretical interest, to the strange electric form factor G s E . The result, A 214.5 6 2.2 ppm, is consistent with the electroweak standard model and no additional contributions from strange quarks. In particular, the measurement implies G s E 1 0.39G s M 0.023 6 0.034͑stat͒ 6 0.022͑syst͒ 6 0.026͑dG n E ͒, where the last uncertainty arises from the estimated uncertainty in the neutron electric form factor. [S0031-9007(98) The proton, which is believed to be a state of three quarks bound by the strong force of quantum chromodynamics (QCD), is a complex object when probed at intermediate energies. In order to develop a useful description, one must first establish all of the relevant degrees of freedom. Recent theoretical and experimental investigations have indicated that strangeness might play an important role [1,2]. For example, do ss pairs contribute to the charge radius or magnetic moment of the proton? It is quite possible, since the mass of the strange quark is comparable to the proton mass and the scale of the strong interaction. On the other hand, the empirically successful 1096 0031-9007͞99͞82(6)͞1096(5)$15.00

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