The superiority of different induction therapies after heartlung and lung transplantation is not clearly established; specifically, whether monoclonal (OKT3) or polyclonal antibody induction therapy provides any advantage. Between 1989 and 1991 we used induction therapy with either rabbit antithymocyte globulin (RATG) or OKT3, given at random based on the availability of RATG. RATG was used in 25 patients (RATG group 1) and OKT3 in 38 patients (OKT3 group 1). Early results suggested a survival advantage with RATG. From 1992 until 1997 we used RATG induction therapy in 108 patients (RATG group 2). This study analyzed longer-term survival, infection, rejection, and obliterative bronchiolitis (OB) rates for RATG group 1 and OKT3 group 1 and assessed outcomes for RATG group 2. The 1-, 3-, and 5-year survival for RATG group 1 was 72 YO, 72 9'0, and 52% and for OKT3 group 1 was 63 YO, 49 %, and 34 Yo (P < 0.05).The 1-and 3-year survival for RATG group 2 was 84 YO and 74 % . The 1-, 3-, and 5-year actuarial freedom rates from Iung rejection for RATG group 1 were 38 YO, 38 YO, and 31 % and for OKT3 group 1 were21Y0,0%,and0% (P<0.01). The linearized rate (eventdl00 patient days) of all infections at 3 months was 1.55 * 0.28 for RATG group 1 and 2.19 i 0.27 for OKT3 group 1 ( P = NS). The infection rate for RATG group 2 was 1.60 f 0.13. The actuarial rates of freedom from OB at 1,3, and 5 years for RATG group 1 were 84 'YO, 51 YO, and 45 YO and for OKT3 group 1 were 77 YO, 61 Y , and 36 YO ( P = NS), while for RATG group 2 the rates were 97 % and 92 Yo at 1 and 3 years ( P < 0.01 vs RATG group 1 and OKT3 group 1). The use of RATG induction therapy from 1989 through 1991 resulted in improved actuarial survival and less rejection, without increased infection rates. The use of RATG since 1992 has continued to result in similar outcomes for survival, infection, and rejection. The time to onset of OB has improved further in recent years. This may be a result of recent improvements in cytomegalovirus (CMV) prophylaxis.