A measurement of the proton spin structure function g(l)(p)(x, Q(2)) in dee
p-inelastic scattering is presented. The data were taken with the 27.6 GeV
longitudinally polarised positron beam at HERA incident on a longitudinally
polarised pure hydrogen gas target internal to the storage ring. The kinem
atic range is 0.021 < x < 0.85 and 0.8 GeV2 < Q(2) < 20 GeV2. The integral
integral(0.021)(0.85) g(l)(p)(x) dx evaluated at Q(0)(2) of 2.5 GeV2 is 0.1
22 +/- 0.003(stat.) +/- 0.010(syst.). (C) Elsevier Science B.V. All rights
reserved.