diff --git a/.github/ISSUE_TEMPLATE.md b/.github/ISSUE_TEMPLATE.md
index 18f32c3a8a5..efaf058c26e 100644
--- a/.github/ISSUE_TEMPLATE.md
+++ b/.github/ISSUE_TEMPLATE.md
@@ -24,4 +24,4 @@ Describe what you expect the output to be. Knowing the correct behavior is also
 Provide any additional information here.
 
 #### Current Version:
-v2.18.0
+v2.18.1
diff --git a/RELEASE-NOTES.txt b/RELEASE-NOTES.txt
index fbe2bedd445..cfc0bea2f68 100644
--- a/RELEASE-NOTES.txt
+++ b/RELEASE-NOTES.txt
@@ -5,6 +5,17 @@ Note: these are the release notes for the stan-dev/stan repository.
 Further changes may arise at the interface level (stan-dev/{rstan,
 pystan, cmdstan}) and math library level (stan-dev/math).
 
+v.2.18.1 (24 December 2018)
+======================================================================
+Bugfix release - major bug in threading where certain thread count and
+job size combinations could result in incorrect output. See
+https://discourse.mc-stan.org/t/bug-in-map-rect-with-threading-in-stan-2-18-0/7056
+for more details.
+
+Bug Fixes
+--------------------------------------------------
+* Fix threading batch size bug (stan-dev/math#1075)
+
 v2.18.0 (13 July 2018)
 ======================================================================
 This is our first release with parallelism (threading and MPI)!
diff --git a/src/docs/reference-manual/statements.Rmd b/src/docs/reference-manual/statements.Rmd
index c9c26a8817e..28f0b25ac78 100644
--- a/src/docs/reference-manual/statements.Rmd
+++ b/src/docs/reference-manual/statements.Rmd
@@ -150,7 +150,7 @@ An assignment statement consists of a variable (possibly multivariate
 with indexing information) and an expression.  Executing an
 assignment statement evaluates the expression on the right-hand side
 and assigns it to the (indexed) variable on the left-hand side.
-An example of a simple assignment is as follows.^[In versions of Stan before 2.18.0, the operator `<-` was used for assignment rather than using the equal sign `=`.  The old operator `<-` is now deprecated and will print a warning. In the future, it will be removed.]
+An example of a simple assignment is as follows.^[In versions of Stan before 2.17.1, the operator `<-` was used for assignment rather than using the equal sign `=`.  The old operator `<-` is now deprecated and will print a warning. In the future, it will be removed.]
 
 ```stan
 n = 0;
diff --git a/src/doxygen/doxygen.cfg b/src/doxygen/doxygen.cfg
index a703576d6d3..2d89df93733 100644
--- a/src/doxygen/doxygen.cfg
+++ b/src/doxygen/doxygen.cfg
@@ -38,7 +38,7 @@ PROJECT_NAME           = "Stan"
 # could be handy for archiving the generated documentation or if some version
 # control system is used.
 
-PROJECT_NUMBER         = 2.18.0
+PROJECT_NUMBER         = 2.18.1
 
 # Using the PROJECT_BRIEF tag one can provide an optional one line description
 # for a project that appears at the top of each page and should give viewer a
diff --git a/src/stan/version.hpp b/src/stan/version.hpp
index 345396ed451..0c6a1a127d2 100644
--- a/src/stan/version.hpp
+++ b/src/stan/version.hpp
@@ -13,7 +13,7 @@
 
 #define STAN_MAJOR 2
 #define STAN_MINOR 18
-#define STAN_PATCH 0
+#define STAN_PATCH 1
 
 namespace stan {
 
diff --git a/src/test/unit/version_test.cpp b/src/test/unit/version_test.cpp
index 8aff9bf1317..71ef6ab5736 100644
--- a/src/test/unit/version_test.cpp
+++ b/src/test/unit/version_test.cpp
@@ -4,11 +4,11 @@
 TEST(Stan, macro) {
   EXPECT_EQ(2, STAN_MAJOR);
   EXPECT_EQ(18, STAN_MINOR);
-  EXPECT_EQ(0, STAN_PATCH);
+  EXPECT_EQ(1, STAN_PATCH);
 }
 
 TEST(Stan, version) {
   EXPECT_EQ("2", stan::MAJOR_VERSION);
   EXPECT_EQ("18", stan::MINOR_VERSION);
-  EXPECT_EQ("0", stan::PATCH_VERSION);
+  EXPECT_EQ("1", stan::PATCH_VERSION);
 }