1. Sulfur contents of each fractions (ethanol soluble and insoluble, and hot water insoluble) of Porphyra tenera were almost stationary throughout the culture.
2. Aspects of sulfur uptake in various fractions of Porphyra tenera were as like as those of UIva pertusa.
3. Under light, sulfur uptake by Porphyra was very active, but under darkness it was very dull, particularly in ethanol insoluble fraction.
4. In Porphyra and Gracilaria, a considerable amount of 35S of the non-adsorbable was incorporated into taurine, while in Monostroma it was incorporated into Dcysteinolic acid.