Introduction: Studies have not established timing of immunoprophylaxis (Rx) with 6-MP, azathioprine, or mesalamine after surgery for CD. Some suggest Rx should be initiated ≤1 month, others advocate targeted Rx at time of endoscopic recurrence. We compare efficacy of these competing approaches.Methods: 199 CD patients who underwent ileocecectomy 9/93 - 4/08 were retrospectively divided into 3 groups based on Rx timing: immediate (I-rx), tailored (T-rx), none (N-rx) . Groups were compared for differences in demographics, pathology, surgical technique (chi square, ANOVA). Rate of symptomatic recurrence (chi-square), and time to symptomatic recurrence was analyzed (log rank, multivariate Cox proportional hazards).Results: 69 (34.7 %) received I-rx, 32 (16.1%) received T-rx and 98 (49.3%) were N-rx. The groups were similar, though I-rx were younger and N-rx more likely to be lost to follow-up (table). At 5-years, 62 (53.9%) patients had endoscopic, 46 (51.9%) had symptomatic and 22(24.3%) had surgical recurrences. On chi square, T-rx appeared more likely than I-rx to have symptomatic recurrence (43.7% vs. 28.9%, p=0.02), but when censored for length of follow up, the only predictor of symptomatic recurrence was CCI (p=0.048). Timing of Rx (p=0.44), age (p=0.07), history of prior resection (p=0.22), presence of active disease (p=0.32) and type of anastomosis (p=0.29) were not. Conclusion: Patients offered immunoprophylaxis tailored to endoscopic recurrence have a similar time to symptomatic recurrence as those offered immunoprophylaxis immediately.

	I-Rx (%)	T-Rx (%)	N-RX (%)	P Value
Male	52	50	51	0.97
Age (yrs)	30.7	33.4	40.7	0.01*
CCI	2.4	3.8	2.2	0.09
Prior Resection	31.8	21.8	26.5	0.54
Disease: Active Fibrostenotic Penetrating	75.4 59.4 68.1	87.5 50 50.0	88.6 60.8 66.7	0.05* 0.53 0.17
Positive Margins	15.9	18.8	22.9	0.50
Stapled Anastomosis	63.7	59.4	73.5	0.03*
Length Follow-Up (yrs)	2.7	3.4	2.2	0.09
Lost to Follow-Up	11.6	9.4	36.7	0.01*