OBJECTIVES: Multi-morbidity (MM) and readmissions in less than 30 days (ReH) require standarized data, diffficult for Argentina. To measure the economic implications, we evaluated if MM determined direct medical costs of ReH. METHODS: In cross sectional study of 1 year hospital discharges (Value in Health;14 (2011):A18), of patients ≥19 yrs old, primary diagnosis (Dx1) and secondary diagnosis (Dx2), total costs (CT$) mean and median per discharge cost ($, 25P-75P-percentiles), in international dollars PPP, (UN Data: 1Arg$ = 1.608 I$ PPP, 2008) were obtained. To measure of multi-morbidity (MM) we used chronic conditions table in (CC+) counts as positive (CC+) per 2Dx. The 30day readmissions (ReH<30) defined as: 1) any readmission within 30 days and 2) the number of stays with at least one subsequent hospital stay within 30 days(strict definition) (ReHs) . RESULTS: In a universe of 45466 discharges, we found 7286 ReH <30 d among adults (≥19 yrs old). Total cost of ReH TC$ 68 145 431I$; mean cost per discharge ($) was 9629 I$ (SD I$ 23 344); Median cost per discharge 4211 I$; (Q1: 1755 -Q3:9291 I$), taken as baseline values for ReH (ReHs is N= 6018; with I$ of 10 600 -SD I$ 25271) . Stratified against MM as 2Dx1, N=3357, mean discharge cost was I$ 10823 (SD I$ 24005); 1,12 times the value of all ReH. MM at 2Dx5, N=718, I$ 16538 (SD I$ 36839); 1,72; and when MM was in 2Dx8, N=137, I$ 18785 (SD I$ 34764); 1,95 times baseline (p trend <0.01). ReHs reduce total number of readmissions and produce slightly higher costs (full data not shown), e.g. in MM of 2Dx8, ReHs is N=130, mean discharge cost I$ 19 052 (SD I$ 35591); 1,80 times baseline. CONCLUSIONS: This first estimate of ReH<30 costs, sensible duration, and demonstrates impact of multi-morbidity (MM) with the method used.