The process of light-adaptation with an intense illumination was examined in the carp horizontal cell by using a new approach comprised of two steps. First, light was periodically modulated by pseudo-white-noise and applied to the retina. Second, the statistical properties of reponses corresponding to one cycle (2.5 sec in this study) of stimuli at different times were examined. Our experiments and analyses gave the following results. The dark-adapted L-cells responded with a sudden initial hyperpolarization followed by a small fluctuation superimposed on the slowly declining steady potential. As light-adaptation proceeded, the response fluctuation gradually increased, then slowly decreased and leveled off. During about the first 1 min of light-adaptation, the amplitude distribution of responses departed from normal distribution in symmetry as well as peakedness, then it rapidly approached normal distribution. The equivalent bandwidth of the power spectrum increased monotonically for about 3 min of light-adaptation but then attained a steady state level (45 Hz). The initial increase of the power at high frequencies was related to the nonlinearity and was probably produced in relation to the power at low frequencies. On the other hand, the later increase of the power at high frequencies implies that the cell became to respond to the high frequency components of the stimulating light.