The photosynthetic microalga Haematococcus pluvialis, a potential source of astaxanthin, was cultivated under illumination with LEDs emitting red (lambda(max) = 625 nm), green(lambda(max) = 525 nm), blue (lambda(max) = 470 nm), blue-purple (lambda(max) = 410 nm) and purple (lambda(max) = 380 nm) light and a fluorescent lamp, and the effects of wavelength on cell growth and astaxanthin accumulation were studied. LEDs emitting light of short wavelengths (380-470 nm) were found to induce astaxanthin accumulation of up to 5-6% per dry cell, although the induction caused the suppression of cell growth. From these results, we proposed a new strategy of cultivating H. pluvialis under illumination with red LEDs without inducing a high level of astaxanthin accumulation, and then switching to illumination with blue LEDs at a high light intensity to induce a high level of astaxanthin accumulation. (C) 2004 Elsevier Inc. All rights reserved.