The value of M̄w for a sample of natural rubber from fresh latex of one clonal type is ∼2 × 106. As the latex ages, M̄w diminishes and the gel content increases. Solutions of samples which have been masticated in oxygen contain very small particles of rubber, the existence of which is demonstrated by both light-scattering and electron-microscope measurements. The particles are heterodisperse and have a mean diameter of about 1000 A. As a result of their small size they are swollen very little in good solvents. They originate from the gel phase and either they are a product of mastication or, more probably, they are latex particles which have survived mastication.