Experimental studies of the Comorosan effect are presented for the LDH-mediated interconversions of lactate and pyruvate. Consistent with the findings of the Comorosan group, the rate of the lactate/LDH reaction was found increased for crystalline lithium lactate irradiated with green light for times t comprising the manifold t = 15+30n sec, n = 0,1,2... However, no upper limit to the number of activating times was encountered although the Comorosan group has always obtained only six such activations. The pyruvate/LDH reaction rate was found enhanced for crystalline sodium pyruvate irradiated t = 5+30n sec. Sharpness of activations for 5-sec and 65-sec irradiated samples was investigated and found to occur only within approximately +/- 0.5 sec of 5.0 and 65.0 sec, slightly broader than the +/- 0.15-sec peak reported by Comorosan for the 5-sec signal. The data contribute to the credibility of the phenomenon but reveal sensitivity of some properties to individual laboratory or procedural factors. The first support is provided for the "discriminating function" component of Comorosan's metabolic control hypothesis.