Geologically 10% of Sri Lanka is made up of Miocene limestone, which covers the northern and northwestern coastal belt of the island. It is used as a raw material for various industries, but at present only cement and lime are used for the construction industry. Therefore the author carried out a series of laboratory tests to determine the mechanical properties of limestone in Sri Lanka, with the aim of determining the suitability of Miocene limestone as aggregate for the construction industry. Borehole samples (NX size) of limestone were obtained from various drilling sites, and tests for physical and mechanical properties and ultrasonic wave velocities were carried out according to ASTM Standards at geotechnical and materials testing laboratories. According to the Los Angeles abrasion value (LAAV) and aggregate impact value (AIV) this limestone may be suitable as the base course material for road construction but may not be suitable for use as the surface material of highways or as railroad ballast. Ultrasonic wave velocities indicate that the limestone is highly compacted and solid. According to the compressive strength of solid limestone, buildings a few storeys high can be constructed on it after a detailed site investigation.