Context: .During the past years photometric surveys, later complemented by follow-up radial-velocity measurements, have revealed the presence of several new extra-solar transiting planets, in very short-period orbits. Many of the host stars are extremely faint (V˜16), making high-precision spectroscopic measurements challenging. Aims: .We used the UVES spectrograph (VLT-UT2 telescope) to obtain high-resolution spectra of 5 stars hosting transiting planets, namely for OGLE-TR-10, 56, 111, 113, and TrES-1. The immediate objective is to derive accurate stellar parameters and chemical abundances. Methods: .The stellar parameters were derived from an LTE analysis of a set of Fe I and Fe II lines. Results: .Complementing the spectroscopic information with photometric transit curves and radial-velocity data from the literature, we then refined the stellar and planetary radii and masses. The obtained data were also used to study the relation between the stellar metallicity and orbital period of the planets.