The essential fatty acid deficiency (EFA) gives rise to many pathologic states and may predispose for certain disease development. One of the most frequently deficient EFA is gamma-linolenic acid. The gamma-linolenic acid supplementation brings some hopeful effects in treatment of diabetic neuropathy, eczema, cyclic mastalgia, rheumatoid arthritis, osteoporosis and ADHD. Many double blind trials have been performed for defective assessment of GLA efficiency. Some of them have proved statistically significant efficacy, the others have led to some doubts. There is a necessity to perform more trials. The gamma-linolenic acid is completely safe, non-toxic, and non-cancerogenic substance. It can be an interesting alternative for supporting treatment.