diff --git a/include/boost/math/special_functions/detail/lanczos_sse2.hpp b/include/boost/math/special_functions/detail/lanczos_sse2.hpp
index df1a04743..2ebde18e0 100644
--- a/include/boost/math/special_functions/detail/lanczos_sse2.hpp
+++ b/include/boost/math/special_functions/detail/lanczos_sse2.hpp
@@ -51,6 +51,15 @@ inline double lanczos13m53::lanczos_sum<double>(const double& x)
       static_cast<double>(23531376880.41075968857200767445163675473L),
       static_cast<double>(0u)
    };
+
+   static const double lim = 4.31965e+25; // By experiment, the largest x for which the SSE2 code does not go bad.
+
+   if (x > lim)
+   {
+      double z = 1 / x;
+      return ((((((((((((coeff[24] * z + coeff[22]) * z + coeff[20]) * z + coeff[18]) * z + coeff[16]) * z + coeff[14]) * z + coeff[12]) * z + coeff[10]) * z + coeff[8]) * z + coeff[6]) * z + coeff[4]) * z + coeff[2]) * z + coeff[0]) / ((((((((((((coeff[25] * z + coeff[23]) * z + coeff[21]) * z + coeff[19]) * z + coeff[17]) * z + coeff[15]) * z + coeff[13]) * z + coeff[11]) * z + coeff[9]) * z + coeff[7]) * z + coeff[5]) * z + coeff[3]) * z + coeff[1]);
+   }
+
    __m128d vx = _mm_load1_pd(&x);
    __m128d sum_even = _mm_load_pd(coeff);
    __m128d sum_odd = _mm_load_pd(coeff+2);
@@ -136,6 +145,15 @@ inline double lanczos13m53::lanczos_sum_expG_scaled<double>(const double& x)
          static_cast<double>(56906521.91347156388090791033559122686859L),
          static_cast<double>(0u)
    };
+
+   static const double lim = 4.76886e+25; // By experiment, the largest x for which the SSE2 code does not go bad.
+
+   if (x > lim)
+   {
+      double z = 1 / x;
+      return ((((((((((((coeff[24] * z + coeff[22]) * z + coeff[20]) * z + coeff[18]) * z + coeff[16]) * z + coeff[14]) * z + coeff[12]) * z + coeff[10]) * z + coeff[8]) * z + coeff[6]) * z + coeff[4]) * z + coeff[2]) * z + coeff[0]) / ((((((((((((coeff[25] * z + coeff[23]) * z + coeff[21]) * z + coeff[19]) * z + coeff[17]) * z + coeff[15]) * z + coeff[13]) * z + coeff[11]) * z + coeff[9]) * z + coeff[7]) * z + coeff[5]) * z + coeff[3]) * z + coeff[1]);
+   }
+
    __m128d vx = _mm_load1_pd(&x);
    __m128d sum_even = _mm_load_pd(coeff);
    __m128d sum_odd = _mm_load_pd(coeff+2);
diff --git a/include/boost/math/special_functions/gamma.hpp b/include/boost/math/special_functions/gamma.hpp
index 417a67426..04dd71316 100644
--- a/include/boost/math/special_functions/gamma.hpp
+++ b/include/boost/math/special_functions/gamma.hpp
@@ -277,7 +277,11 @@ T lgamma_imp(T z, const Policy& pol, const Lanczos& l, int* sign = 0)
       T zgh = static_cast<T>(z + Lanczos::g() - boost::math::constants::half<T>());
       result = log(zgh) - 1;
       result *= z - 0.5f;
-      result += log(Lanczos::lanczos_sum_expG_scaled(z));
+      //
+      // Only add on the lanczos sum part if we're going to need it:
+      //
+      if(result * tools::epsilon<T>() < 20)
+         result += log(Lanczos::lanczos_sum_expG_scaled(z));
    }
 
    if(sign)
diff --git a/test/test_gamma.hpp b/test/test_gamma.hpp
index f259e963a..47cd3d5eb 100644
--- a/test/test_gamma.hpp
+++ b/test/test_gamma.hpp
@@ -324,5 +324,14 @@ void test_spots(T, const char* name)
       BOOST_CHECK_EQUAL(boost::math::tgamma(-std::numeric_limits<T>::denorm_min()), -std::numeric_limits<T>::infinity());
       BOOST_CHECK_EQUAL(boost::math::tgamma(std::numeric_limits<T>::denorm_min()), std::numeric_limits<T>::infinity());
    }
+   //
+   // Extra large values for lgamma, see https://github.com/boostorg/math/issues/242
+   //
+   if (boost::math::tools::digits<T>() >= std::numeric_limits<double>::digits)
+   {
+      BOOST_CHECK_CLOSE(::boost::math::lgamma(ldexp(static_cast<T>(11103367432951928LL), 32)), static_cast<T>(2.7719825960021351251696385101478518546793793286704974382373670822285114741208958e27L), tolerance);
+      BOOST_CHECK_CLOSE(::boost::math::lgamma(ldexp(static_cast<T>(11103367432951928LL), 62)), static_cast<T>(4.0411767712186990905102512019058204792570873633363159e36L), tolerance);
+      BOOST_CHECK_CLOSE(::boost::math::lgamma(ldexp(static_cast<T>(11103367432951928LL), 326)), static_cast<T>(3.9754720509185529233002820161357111676582583112671658e116), tolerance);
+   }
 }