This paper is the second in a series describing the Sydney University Molonglo Sky Survey ( SUMSS ) being carried out at 843 MHz with the Molonglo Observatory Synthesis Telescope ( MOST ) .
The survey will consist of \sim 590 4.3 ^ { \circ } \times 4.3 ^ { \circ } mosaic images with 45 ^ { \prime \prime } \times 45 ^ { \prime \prime } cosec| \delta| resolution , and a source catalogue .
In this paper we describe the initial release ( version 1.0 ) of the source catalogue consisting of 107,765 radio sources made by fitting elliptical gaussians in 271 SUMSS 4.3 ^ { \circ } \times 4.3 ^ { \circ } mosaics to a limiting peak brightness of 6 mJy beam ^ { -1 } at \delta \leq - 50 ^ { \circ } and 10 mJy beam ^ { -1 } at \delta > -50 ^ { \circ } .
The catalogue covers approximately 3500 deg ^ { 2 } of the southern sky with \delta \leq - 30 ^ { \circ } , about 43 per cent of the total survey area .
Positions in the catalogue are accurate to within 1 ^ { \prime \prime } -2 ^ { \prime \prime } for sources with peak brightness A _ { 843 } \geq 20 mJy beam ^ { -1 } and are always better than 10 ^ { \prime \prime } .
The internal flux density scale is accurate to within 3 per cent .
Image artefacts have been classified using a decision tree , which correctly identifies and rejects spurious sources in over 96 per cent of cases .
Analysis of the catalogue shows that it is highly uniform and is complete to 8 mJy at \delta \leq - 50 ^ { \circ } and 18 mJy at \delta > -50 ^ { \circ } .
In this release of the catalogue about 7000 sources are found in the overlap region with the NRAO VLA Sky Survey ( NVSS ) at 1.4 GHz .
We calculate a median spectral index of \alpha = -0.83 between 1.4 GHz and 843 MHz .
This version of the catalogue will be released via the World Wide Web with future updates as new mosaics are released .