IVF treatment, which involves ovarian stimulation, poses significant health problems such as ovarian hyperstimulation and is associated with a high incidence of multiple pregnancy and premature birth. In this paper, we demonstrate how natural cycle IVF is an effective and potentially cost-effective alternative treatment option for certain groups of infertile couples. The study was conducted in the Assisted Conception Unit at King's College School of Medicine, London. Fifty-two women with regular menstrual cycles whose partners had normal semen parameters were offered a total of 181 cycles of treatment (average 3.49 per couple). Life table analysis was used to calculate cumulative success rates after successive cycles of treatment. After four cycles, the cumulative probability of pregnancy was 46% with an associated live birth rate of 32%. To achieve maximal effectiveness, natural cycle IVF should be offered as a series of treatment cycles, for it is safer, less stressful and can be offered over consecutive cycles. Moreover, the avoidance of expensive drugs and reduced intensity of monitoring make natural cycle IVF less expensive than conventional treatment involving stimulation. We calculate that this treatment can be offered at approximately 23% of the cost of a stimulated cycle, suggesting that it may be a cost-effective alternative to conventional assisted conception techniques.