In this Letter we discuss a bistable model driven by two white noise sources, when the correlation time of the correlations between two sources t is nonzero. We find that there is a critical value of the correlation time t c . For t . t c , the system undergoes a succession of two phase transitions (namely, the reentrance phenomenon) as the strength of the correlations between two noise sources l is varied. However, for t , t c , the system undergoes a (single) phase transition as l is varied.[S0031-9007(96)01943-6] PACS numbers: 05.40.+j, 82.20.Db The study of dynamical systems disturbed by noise is recurrent in many contexts of physics and other sciences. Particularly for nonequilibrium systems, where noise plays a crucial role[1,2], the noise-induced transition has been intensively investigated. The effects of colored noise (i.e., fluctuations of intensity D with a correlation time t) have attracted a great deal of interest in recent years. Different theories have been used to deal with the colored-noise problem, for instance, the conventional small-t theory [3,4], the functional-calculus theory of Fox [5], the decoupling theory (often called Hanggi ansatz) [6], the unified colored-noise theory [7], and the recent interpolation procedure [8].Recently, Castro et al. [9] presented an analysis of a chemical reaction system, when it is forced by one colorednoise source, by using the interpolation procedure which is an extension of the unified colored-noise theory and allows us to study both t ! 0 and t !`cases. They showed that the system undergoes a purely noise-induced transition from a monostable regime to a bistable one, then to the monostable regime as t increases, namely, a succession of two phase transitions when the correlation time is monotonically varied. This type of nonequilibrium transitions phenomenon has been called the reentrance phenomenon [9].The largest amount of work about fluctuations has been referred to the consideration of systems with just one noise source. However, more realistic models of physical systems require considering various noise sources, for example, the laser models [10], the lattice model [11], the structure-formation process in liquid crystals [12], the imperfect pitchfork bifurcation in superfluid turbulence in liquid helium [13], etc. Though various sources are presented simultaneously in some stochastic processes, they are assumed to have different origins and are treated as independent random variables in most of the previous investigations [10 -15]. However, in certain situations they may have a common origin and thus may be correlated with each other as well [16][17][18][19][20][21]. The study of dynamical systems with correlation noise terms has attracted attention in the field of stochastic processes. Some of these investigations were concerned with the steady-state statistical properties of systems [16 -20]; others were concerned with the transient problems [21]. Now a question to be raised is if similar peculiarities studied by Castro et al. [9] can be found in...