A review of the literature reveals that although the effects of environmental degradation have been incorporated into some recent finite element stress analyses of adhesive joints, closed form solutions have not yet been developed. Due to its ease of use, such a closed form approach would be very useful for screening analyses of potential joint configurations. Two different closed form approaches have been developed. Both use simple, yet demonstrably reasonable, assumptions about the affect of moisture on the mechanical properties of the adhesive and both use a Fickian diffusion model to determine moisture distribution in the joint. The simplest approach is based on limit state assumptions and results in a simple non-dimensionalised equation relating residual strength to the time of exposure. The equation is in the form of an infinite series and is also presented as a design chart for even easier access. The second approach is the adaptation of a generalised non-linear adhesive sandwich analysis. The advantage of this is that it is applicable to a wide range of bonded joints and not just the single lap joint in the closed form solution. Further, it is not limited by limit state assumptions and gives the adhesive peel and shear stress distribution for any loading condition and exposure time. Both approaches were illustrated by the application to a typical single lap joint, exposed at 85% RH for 230 days.