The DNA content per gram of wet hepatopancreas and green gland of Panulirus argus was found to vary with molt stage. In hepatopancreas of premolt and postmolt spiny lobsters, the DNA content was, respectively, 5-fold and 3-fold higher than in intermolt animals. Green gland DNA content showed a trend of varying in the same manner as hepatopancreas DNA. The DNA content per gram of wet green gland from intermolt lobsters averaged about 50 times higher than that of hepatopancreas. The changes in DNA content were not related to changes in wet tissue weights during the molting cycle. The ratio of hepatopancreas or green gland wet weights to total body weight remained constant. A ribosomal DNA probe hybridized to intermolt hepatopancreas DNA samples to a much greater extent than to premolt or postmolt samples, suggesting that rDNA sequences are under-represented in the amplified DNA which occurs prior to ecdysis.