1. Flory’s theory on molecular size distribution in linear condensation polymers was applied to linear synthetic polyamides. 2. Viscosities of polyhexamethylene adipamide or polycapramide in m-cresol are expressed by Fickentscher’s equation. 3. The application of the Staudinger viscosity relation to polyamide was discussed. 4. The relations between intrinsic visocisty and “weight average” molecular weight were established experimentally from Flory’s theory and the freezing point depression measurement of phenolic solution. 5. The time dependence of the degree of depolymerization was discussed under the assumption that the rate at which bonds are cut is proportional to the number of uncut bonds in the system.