  A major goal of the RHIC spin program is to measure \Delta g, the gluon
contribution to the proton's spin. Measurements by PHENIX of the double
longitudinal spin asymmetry, A_LL, of the neutral pion production at
mid-rapidity in polarized proton collisions have been shown to constrain \Delta
g. Results from the 2005 RHIC run, as well as high p_T data from the 2006 RHIC
run, are presented. The results disfavor maximal positive and negative values
of \Delta g. A measurement of azimuthally independent double transverse spin
asymmetry, A_TT, is also presented.
