Abstract.The main result of this paper is as follows. Given functions <#>,(f).... ,r>,,(e) which are holomorphic in sectors S.S", respectively, where S¡ U ■ ■ • US, = {c: |argE|<7r/2a, 0 <|e|< p} for a > 1, p > 0, set ,A = $, -4>k if S, n Sk ¥= 0. Then {4>/k} satisfy cocycle conditions /k + kl = ;/ whenever S; PI Sk nS,^ 0. In addition to the conditions |J< MQ and \r\< M0 on the two rays of the boundary (i.e. arg e = w/2 a ), and |^;(e)|< A exp(c/|e|) in S; for some positive numbers A and c, j = l,2,...,c, if the {<¡>;} satisfy the conditions |,|< M on S,, 7 = 1,2.c (From the cohomological point of view, we can get global results for ;, once the local data on cocycles is known.)1. Introduction. Let ß = (e: -it/2a < arg e < w/2a, 0 <|e|< p} be a sector in the right half complex e-plane, where a > 1 and p is a positive number. Let / be a complex valued function which is continuous on ß* = {e: -7r/2a < arg e < ir/2a, 0 <|e|=s p}, holomorphic in ß, and there are positive constants M and c such that |/(e) |< Mexp(c/|e |) for all e G ß. Assume, furthermore, that |/(e) |< M for all e on the boundary of ß. Then, the Phragmen-Lindelöf theorem states that |/(e)|=£ M for all e in ß (see [2, p. 282]). In this paper, we shall generalize this theorem in a cohomological form; i.e. given functions <£,(£),... ,"(e) which are holomorphic in sectors S,,... ,S", respectively, ß = Sx U • • ■ U 5"", set k if Sj C\ Sk¥= 0. Then {>,*} satisfy cocycle conditions k/ = d>7 whenever S, D Sk C\ S¡ ¥^ 0. With this property, our theorem can be stated in the following way: If the {<£•} satisfy the conditions |" |< M0 on the two rays of the boundary (i.e. arg e = ±tr/2a), then we get I.|< M on Sj,j = l,...,v (cf. Theorem 1). From the cohomological point of view, we can get global results for