  This contribution reports on a proof-of-principle measurement of the
longitudinal spin transfer $D_{LL}$ in inclusive $\Lambda$ and $\bar \Lambda$
production in polarized proton-proton collisions at a center of mass energy
$\sqrt{s}$ = 200 GeV. The data sample consists of about 3 $\times$ $10^6$
minimum bias events collected in the year 2005 by the STAR experiment at RHIC
with proton beam polarizations of up to 50%. The $\Lambda$($\bar \Lambda$)
candidates are reconstructed at mid-rapidity ($|\eta|<1$) using the STAR Time
Projection Chamber via the dominant decay channel $\Lambda\to p \pi^-$ ($\bar
\Lambda \to \bar p \pi^+$). Their mean transverse momentum $p_T$ is about 1.3
GeV/c and longitudinal momentum fraction $x_F = 7.5 \times 10^{-3}$ . The
longitudinal $\Lambda$($\bar \Lambda$) polarization is determined using a
method in which the detector acceptance mostly cancels.
