Averages of $b-$hadron properties as of summer 2004

This article reports world averages for measurements on $b$-hadron properties obtained by the Heavy Flavor Averaging Group (HFAG) using the available results as of summer 2004 conferences. In the averaging, the input parameters used in the various analyses are adjusted (rescaled) to common values, and all known correlations are taken into account. The averages include b-hadron lifetimes, $B$-oscillation (mixing) parameters, semileptonic decay parameters, rare decay branching fractions, and CP violation measurements.