This study examined the temporal relationships between index discharges from hospital and emergency readmissions in the area covered by the Oxford record linkage study in the years 1975-84. We report data on 204, 856 readmissions. Index admissions were grouped into elective and immediate categories and into medical and surgical specialty groups. The time intervals between elective prostatectomy or emergency appendicectomy and emergency readmissions were also examined as examples of specific operations. Readmissions clustered strikingly in the first few weeks following discharge. Over a third of emergency readmissions in the year following discharge occurred in the first four weeks. This close temporal proximity indicates that emergency readmissions are generally associated with the first index admission and therefore that emergency readmissions are appropriate topics for further investigation through health services research and medical audit.