The far infrared nebular spectrum provides a valuable complement to the observed lines in other spectral regions. There are several reasons for this, the most important being the large increase in the number of ions observed, and the fact that the abundances found from these lines are relatively insensitive to the electron temperature. This leads to a more accurate determination of the abundances. To date, twelve PN have had abundances determined in this way. These results are summarized. The evolution of the central star is discussed in the light of these results.