Context :

Aims : We present the first public release of high-quality data products ( DR1 ) from Hi-GAL , the Herschel infrared Galactic Plane Survey .
Hi-GAL is the keystone of a suite of continuum Galactic Plane surveys from the near-IR to the radio , and covers five wavebands at 70 , 160 , 250 , 350 and 500 \mu m , encompassing the peak of the spectral energy distribution of cold dust for 8 \lesssim T \lesssim 50K .
This first Hi-GAL data release covers the inner Milky Way in the longitude range 68 ^ { \circ } \gtrsim \ell \gtrsim - 70 ^ { \circ } in a |b| \leq 1 ^ { \circ } latitude strip .

Methods : Photometric maps have been produced with the ROMAGAL pipeline , that optimally capitalizes on the excellent sensitivity and stability of the bolometer arrays of the Herschel PACS and SPIRE photometric cameras , to deliver images of exquisite quality and dynamical range , absolutely calibrated with Planck and IRAS , and recovering extended emission at all wavelengths and all spatial scales , from the point-spread function to the size of an entire 2 ^ { \circ } \times 2 ^ { \circ } ” tile ” that is the unit observing block of the survey .
The compact source catalogues have been generated with the CuTEx algorithm , specifically developed to optimize source detection and extraction in the extreme conditions of intense and spatially varying background that are found in the Galactic Plane in the thermal infrared .

Results : Hi-GAL DR1 images are cirrus-noise-limited , reaching the 1 \sigma -rms predicted by the Herschel Time Estimators for parallel-mode observations at 60 ^ { \prime \prime } s ^ { -1 } scanning speed only in relatively low cirrus emission regions .
Hi-GAL DR1 images will be accessible via a dedicated web-based image cutout service .
The DR1 Compact Source Catalogues are delivered as single-band photometric lists containing , in addition to source position , peak and integrated flux and source sizes , a variety of parameters useful to assess the quality and reliability of the extracted sources ; caveats and hints to help this assessment are provided .
Flux completeness limits in all bands are determined from extensive synthetic source experiments and greatly depend on the specific line of sight along the Galactic Plane , due to the greatly varying background as a function of Galactic longitude .
Hi-GAL DR1 catalogues contain 123210 , 308509 , 280685 , 160972 and 85460 compact sources in the five bands , respectively .

Conclusions :