The structure of clusters of rhodium and palladium atoms formed on W(011) by deposition below and above the adatom migration temperature, as well as upon subsequent annealing of the films in the range T an=100–1000 K, is studied by conventional and video low-energy electron diffraction (LEED) for various submonolayer coverages. Films deposited below the single-adatom migration temperature show a predominantly random distribution of adatoms over the adsorption sites with some signs of order, evidencing mobility anomalous for single adatoms. Upon annealing, the structure of the films acquires long-range order and undergoes a set of irreversible phase transitions. Two types of adatom cluster are found: one-dimensional densely packed chains aligned along the substrate 〈111〉 directions and two-dimensional densely packed islands. The parameters of the cluster structure, such as interatomic and interchain spacing, chain length and temperature range of stability, are derived from LEED intensity profiles. The cluster structures and phase transitions are discussed in terms of indirect interactions between adatoms. The work function changes are measured with the contact potential difference method as a function of coverage and annealing temperature. The correlation between work function changes and phase transitions is determined.