  We present a chemical composition analysis of 36 giants in the nearby mildy
metal-poor (<[Fe/H]> = -1.18) "CN-bimodal" globular cluster M4. Confronted with
a cluster that has large and variable interstellar extinction across the
cluster face, we combined traditional spectroscopic abundance methods with
modifications to line-depth ratio techniques to determine the atmospheric
parameters of our stars. We derive a total-to-selective extinction ratio of 3.4
and an average <E(B-V)> reddening of 0.33 which is significantly lower than
that estimated by using the dust maps made by Schlegel et al. (1998).
  Abundance ratios for Sc, Ti, V, Ni, & Eu are typical of halo field and
cluster stars. However, Si, Al, Ba, & La are overabundant with respect to what
is seen in other globular clusters of similar metallicity. Superimposed on the
primordial abundance distribution is evidence for the existence of
proton-capture synthesis. We recover some of the C, N, O, Na, Mg, & Al
abundance swings and correlations found in other more metal-poor globular
clusters but the range of variation is muted. The Al enhancements appear to be
from the destruction of 25,26Mg, not 24Mg. The C+N+O abundance sum is constant
to within the observational errors, and agrees with the C+N+O total that might
be expected for M4 stars at birth.
  The M4 AGB stars have C,N,O abundances that show less evidence for proton-
capture nucleosynthesis than is found in the less-evolved stars of the RGB.
Deeply-mixed stars of the RGB, subsequent to the helium core flash, might take
up residence on the blue end of the HB, and thus fail to evolve back to the AGB
but reasons for skepticism concerning this scenario are noted.
