This chapter discusses the properties and interactions of atomic defects in bismuth (Bi). The atomic structure of bismuth is not very stable i.e. phase transformations are observed after variation of temperature and/or pressure. These phase transformations do often not allow the comparison of low temperature irradiation data with high temperature equilibrium data; in addition the vicinity of a phase transformation may influence defect parameters even at quite distant temperatures. For the semimetals (Bi, Sn) the position of the Fermi-level that changes with temperature and impurity concentrations, can strongly affect the defect properties. The isochronal annealing of Bi semimetal has been investigated by electrical resistivity measurements after electron irradiation, n-irradiation and quenching. PAS has been applied after electron-irradiation at 20 K and after deformation at 77 K. Different annealing temperatures and positron lifetimes have been observed in different investigations these differences have been explained by shifts of the Fermi level due to impurities and all interpretations are therefore to be considered as temptative. The galvanomagnetic properties of point defects in this semimetal have been discussed. No positron trapping has been observed under thermal equilibrium conditions up to the melting point. Properties of Frenkel defects (FD) and vacancies (V) in bismuth are tabulated.