The instantaneous elastic moduli for a nylon-6 monofilament were derived on strain recoveries right after creep, stress relaxation, and rapid elongation,Ec,Es andEe, respectively. It was found that during strain recoveryEs(>Ee) andEe increase monotonically with increasing load,m1, on the sample. The extrapolated value of Es atm1=0 g is almost equal to Young's modulus, 4.06 GPa. The value ofEc also increased with increasingm1, and atm1=600 g (1.93 t cm−2) reached about 14 GPa. The endothermic heat change right after creep, stress relaxation or rapid elongation,Q, was negligibly small. For comparison,Es,Ec andQ were also investigated for silicone rubber. It was found thatEs (53.8 M Pa at the draw ratioD=1.2) decreased abruptly atD=1.3. In the range ofD=1.4–1.9,Es was only 22.6 MPa. In the case of stress relaxation,Q increased with increasingD from 4 J mol−1 (atD=1.2) to 56 J mol−1 (atD=1.9). FurthermoreEc (5.58 MPa atm1=133.8 g (429.4 kg cm−2)) increased gradually with increasing m1 and attained 16.6 MPa atm1=548.4 g (1.76 t cm−2). In the case of creep,Q was in the range of 0–11.5 J mol−1 and larger when larger loads,m2 were removed during the later stages of creep.