  In this paper we report new observations and derive chemical abundances for a
sample of 26 planetary nebulae (PN) located in the anticenter direction. Most
of these nebulae are far away objects, located at galactocentric distances
greater than about 8 kpc, so that they are particularly useful for the
determination of the radial gradients at large distances from the galactic
center. A comparison of the present results with previously determined
abundances suggests that the radial abundance gradients flatten out at
distances larger than about 10 kpc from the center.
