Handsheets from six pulps that varied in their initial content of lignin and hot-1%-alkalisoluble matter were exposed to visible and near ultraviolet radiation from three light sources. Essentially the same behavior was observed under all three. The results indicated that a high initial content of hot-alkali-soluble matter in the cellulose is likely to lead to darkening, while lignin itself tends to bleach. The tendencies to bleach and to darken take place concurrently. An increased percentage of lignin in the pulps will increase the rate at which hot-alkali-soluble matter is developed during exposure. -- AATA