This presentation describes the first determination of bounds on the 
CP-violation paramater 2beta_s using Bs decays in which the flavor of the 
bottom meson at production is identified. The result is based on approximately 
2000 Bs->J/psi phi decays reconstructed in a 1.35 fb-1 data sample collected
with the CDF II detector using ppbar collisions produced at the 
Fermilab Tevatron. We report confidence regions in the two-dimensional space of
2 beta_s and the decay width difference, Delta Gamma. 
Assuming the standard model  predictions of 2 beta_s and Delta Gamma, the
probability of deviation as large as the level of observed data is 15%, 
corresponding to 1.5 Gaussian standard deviations.