Abstract: Environmental factor estimation for the gamma distributionwith two parameters is studied here.In consideration of the characteristicsof the gamma distribution and the definition of environmental factors forthe exponential distribution and the convenience of data converting,the de-finition of environmental factors for the gamma distribution is proposed.In according to this definition,lower and upper confidence limits of environ-mental factors are derived by classical,Bayesian and Fiducial methods,andsome approximate confidence limits are also given.A practical example isprovided.