  We present a preliminary measurement of CP-violation parameters in the decay
B0 -> K+K-K0, using approximately 347 million BBbar events collected by the
BABAR detector at SLAC. Reconstructing the neutral kaon as KS -> pi+pi-, KS ->
pi0pi0, or KL, we analyze the Dalitz plot distribution and measure fractions to
intermediate states. We extract CP parameters from the asymmetries in
amplitudes and phases between B0 and B0bar decays across the Dalitz plot. For
decays to phiK0, we find beta_eff=0.06 +/- 0.16 +/- 0.05, Acp=-0.18 +/- 0.20
+/- 0.10, where the first uncertainty is statistical and the second one is
systematic. For decays to f0K0, we find beta_eff=0.18 +/- 0.19 +/- 0.04,
Acp=0.45 +/- 0.28 +/- 0.10. Combining all KKK0 events and taking account of the
different CP eigenvalues of the individual Dalitz plot components, we find
beta_eff = 0.361 +/- 0.079 +/- 0.037, Acp = -0.034 +/- 0.079 +/- 0.025. The
trigonometric reflection at pi/2 - beta_eff is disfavored at 4.6 sigma. We also
study angular distributions in B0 -> K+K-KS and B+ -> phi K+ decays and measure
the direct CP asymmetry in B+ -> phi K+ decays, Acp = 0.046 +/- 0.046 +/-
0.017.
