The lattice parameter of nearly perfect gallium crystals was measured by x-ray diffraction on (440), (308) and (046) planes between 10°C and 10−4°C close to the melting point. The thermal expansion coefficients in the three main crystallographic directions are 1.33, 3.19 and 1.62 ⋅ 10−5 1/°C without anomalies. The length change was measured between 10°C and about 5 mK below the melting point in (100), (010), and (001) direction. The thermal expansion coefficients in these directions are 1.12, 3.38, and 1.85 ⋅ 10−5 1/°C without anomalies. The change of the vacancy concentration between 283 K and the melting point can be estimated to 4 ⋅ 10−5, the vacancy formation energy to about 0.23 eV. Premelting effects could not be detected.