We report on a new survey for z \approx 4.5 Lyman- \alpha sources , the Large Area Lyman Alpha ( LALA ) survey .
Our survey achieves an unprecedented combination of volume and sensitivity by using narrow-band filters on the new 8192 ^ { 2 } pixel CCD Mosaic Camera at the 4 meter Mayall telescope of Kitt Peak National Observatory .

Well-detected sources with flux and equivalent width matching known high redshift Lyman- \alpha galaxies ( i.e. , observed equivalent width \hbox { EW } > 80 Å , 2.6 < \hbox { ( line + continuum flux ) } / ( 10 ^ { -17 } { erg cm ^ { -2 } s ^ { -1 } } ) < 5.2 , and \delta ( \hbox { EW } ) / \hbox { EW } < 0.25 ) have an observed surface density corresponding to 11000 \pm 700 per square degree per unit redshift at z = 4.5 .
Spatial variation in this surface density is apparent on comparison between counts in 6561 \pm 40 Å and 6730 \pm 40 Å filters .

Early spectroscopic followup results from the Keck telescope included three sources meeting our criteria for good Lyman- \alpha candidates .
Of these , one is confirmed as a z = 4.52 source , while another remains consistent with either z = 4.55 or z = 0.81 .
We infer that 30 to 50 \% of our good candidates are bona fide Lyman- \alpha emitters , implying a net density of \sim 4000 Lyman- \alpha emitters per square degree per unit redshift .