This paper reports on the method and the results of the Drug Tracking Proje
ct, a comprehensive multi-disciplinary database for social, health and crim
inal justice agencies. It analyses overlap between total agency populations
and tracks the progress of all drug and alcohol agency clients in one coun
ty through a range of services to identify the sub-group of "revolving door
" clients who re-use specialist and generic services. Data for the two year
s (Oct. 1996-98) for 97,162 cases show drug agency overlap of 44%, (n = 213
9) and alcohol agency overlap of 54%, (n = 1639.). Of the population of "re
valving door" clients (defined ms those who attended four or five of types
of service) 41% had also attended a drug andlor alcohol agency. The extent
of drug and alcohol problems in selected populations was approximately two
thirds, of which half received specialist treatment. The method has potenti
al to inform multi-agency screening and co-working.