Analysis of the visual fields of 20 glaucoma patients using 229 F2 programmes consisting of 30 degrees long profiles with 1 degree resolution and double measurements of the light sensitivity threshold, revealed that there is a positive correlation between mean loss and mean short-term fluctuations; short-term fluctuations tend to be larger with increasing loss of sensitivity. However, small short-term fluctuations were also seen in areas of greatly reduced sensitivity. Analysis of the F2 programmes showed 12 different abnormal patterns. The pattern most frequently found, "increased scatter with normal sensitivity", appears to be the earliest perimetric sign of glaucoma. Progression of the glaucomatous damage produces a "gray area of increased scatter", usually accompanied by reduced sensitivity with a poorly defined lower and upper threshold.