OBJECTIVES: To evaluate an integrated analysis of bleeding patterns associated with use of the subdermal contraceptive implant Implanon (etonogestrel, Organon, part of Schering-Plough) and to provide physician guidance to optimize patient counselling. METHODS: Data from 11 clinical trials were reviewed (N = 923). Assessments included bleeding-spotting records, dysmenorrhoea, and patient-perceived reasons for discontinuation. Bleeding patterns were analysed via reference period (RP) analyses. RESULTS: Implanon use was associated with the following bleeding irregularities: amenorrhoea (22.2%) and infrequent (33.6%), frequent (6.7%), and/or prolonged bleeding (17.7%). In 75% of RPs, bleeding-spotting days were fewer than or comparable to those observed during the natural cycle, but they occurred at unpredictable intervals. The bleeding pattern experienced during the initial phase predicted future patterns for the majority of women. The group of women with favourable bleeding patterns during the first three months tended to continue with this pattern throughout the first two years of use, whereas the group with unfavourable initial patterns had at least a 50% chance that the pattern would improve. Only 11.3% of patients discontinued owing to bleeding irregularities, mainly because of prolonged flow and frequent irregular bleeding. Most women (77%) who had baseline dysmenorrhoea experienced complete resolution of symptoms. CONCLUSION: Implanon use is associated with an unpredictable bleeding pattern, which includes amenorrhoea and infrequent, frequent, and/or prolonged bleeding. The bleeding pattern experienced during the first three months is broadly predictive of future bleeding patterns for many women. Effective preinsertion counselling on the possible changes in bleeding patterns may improve continuation rates.