A review is presented of techniques cur- rently in use, or being developed, to enable the determination of virgin rock stress at consid- erable depth (> 1000 m) from small diameter sur- face drill holes (< 200 mm dia.). Most of the methods reviewed involve elaborate electronic instrumentation and require highly specialised and costly drilling techniques for their execu- tion. Among them, however, two techniques appear relatively simple in principle and do not involve the use of special drilling tech- niques. These are the Hydraulic Fracturing Pechnique and the Anelastic Strain Relaxation Technique. Laboratory tests have been conducted to investigate the basic premise upon which the Anelastic Strain Relaxation Technique is based._x000D_
Although further laboratory testing is necessary, the results of these early tests seem to indi- cate that the technique may be viable. The re- sults of some simple field trials of the Strain Relaxation Technique conducted in the southern coalfields area of N.S.W. are included.