Contact potential difference (CPD) and surface photovoltage (SPV) has been associated in topographic (110) GaAs surfaces studied in n and p type samples. Measurements are performed in situ on cleaved and submonolayer silver covered surfaces. Acceptor and donor surface states have been found on all these surfaces. For cleaved surfaces, cleavage defects are clearly correlated to states. For silver covered surfaces, Fermi level pinning is effective and results can agree with the unified model for III–V semiconductors proposed by Spicer et al.