  We present K- and L-band photometry obtained with the Keck I telescope for a
representative sample of L and T dwarfs. These observations were motivated in
part by the dominant role water and methane play in shaping the flux near 2 and
3 microns and by the potential use of these bands as indicators of spectral
class in the infrared. In addition, these observations aid the determination of
the bolometric luminosity of L and T dwarfs. Here we report the K, L' and Ls
magnitudes of our objects and the trends observed in the (K-L') and (K-Ls)
colors as a function of L- and T-dwarf spectral class. We compare these colors
with theoretical models, derive a relationship between effective temperature
and L-spectral class, and compare our temperature estimates with others.
