Angular distributions of secondary particles are given in the form f(μ,E), where μ is the cosine of the angle between the incident and emergent particles and E is the energy of the incident particle. This distribution may be defined in either center-of-mass or laboratory systems. The function f may be defined in one of three ways: as a tabulated function of μ, as an expansion of Legendre polynomial or as a constant value over the entire energy range when the distribution is isotropic. The package janus.format.endf.data.angular the classes that store and access angular distribution data that is imported from FILE 4 in ENDF format.