diff --git a/README.md b/README.md
index f32b8c9..7144867 100644
--- a/README.md
+++ b/README.md
@@ -1,8 +1,6 @@
 # Benchmark
 
-Welcome to your new gem! In this directory, you'll find the files you need to be able to package up your Ruby library into a gem. Put your Ruby code in the file `lib/benchmark`. To experiment with that code, run `bin/console` for an interactive prompt.
-
-TODO: Delete this and the text above, and describe your gem
+The Benchmark module provides methods for benchmarking Ruby code, giving detailed reports on the time taken for each task.
 
 ## Installation
 
@@ -22,7 +20,112 @@ Or install it yourself as:
 
 ## Usage
 
-TODO: Write usage instructions here
+The Benchmark module provides methods to measure and report the time used to execute Ruby code.
+
+Measure the time to construct the string given by the expression <code>"a"*1_000_000_000</code>:
+
+```ruby
+require 'benchmark'
+puts Benchmark.measure { "a"*1_000_000_000 }
+```
+
+On my machine (OSX 10.8.3 on i5 1.7 GHz) this generates:
+
+```
+0.350000   0.400000   0.750000 (  0.835234)
+```
+
+This report shows the user CPU time, system CPU time, the sum of the user and system CPU times, and the elapsed real time. The unit of time is seconds.
+
+Do some experiments sequentially using the #bm method:
+
+```ruby
+require 'benchmark'
+n = 5000000
+Benchmark.bm do |x|
+  x.report { for i in 1..n; a = "1"; end }
+  x.report { n.times do   ; a = "1"; end }
+  x.report { 1.upto(n) do ; a = "1"; end }
+end
+```
+
+The result:
+
+```
+    user     system      total        real
+1.010000   0.000000   1.010000 (  1.014479)
+1.000000   0.000000   1.000000 (  0.998261)
+0.980000   0.000000   0.980000 (  0.981335)
+```
+
+Continuing the previous example, put a label in each report:
+
+```ruby
+require 'benchmark'
+n = 5000000
+Benchmark.bm(7) do |x|
+  x.report("for:")   { for i in 1..n; a = "1"; end }
+  x.report("times:") { n.times do   ; a = "1"; end }
+  x.report("upto:")  { 1.upto(n) do ; a = "1"; end }
+end
+```
+
+The result:
+
+```
+              user     system      total        real
+for:      1.010000   0.000000   1.010000 (  1.015688)
+times:    1.000000   0.000000   1.000000 (  1.003611)
+upto:     1.030000   0.000000   1.030000 (  1.028098)
+```
+
+The times for some benchmarks depend on the order in which items are run.  These differences are due to the cost of memory allocation and garbage collection. To avoid these discrepancies, the #bmbm method is provided.  For example, to compare ways to sort an array of floats:
+
+```ruby
+require 'benchmark'
+array = (1..1000000).map { rand }
+Benchmark.bmbm do |x|
+  x.report("sort!") { array.dup.sort! }
+  x.report("sort")  { array.dup.sort  }
+end
+```
+
+The result:
+
+```
+Rehearsal -----------------------------------------
+sort!   1.490000   0.010000   1.500000 (  1.490520)
+sort    1.460000   0.000000   1.460000 (  1.463025)
+-------------------------------- total: 2.960000sec
+            user     system      total        real
+sort!   1.460000   0.000000   1.460000 (  1.460465)
+sort    1.450000   0.010000   1.460000 (  1.448327)
+```
+
+Report statistics of sequential experiments with unique labels, using the #benchmark method:
+
+```ruby
+require 'benchmark'
+include Benchmark         # we need the CAPTION and FORMAT constants
+n = 5000000
+Benchmark.benchmark(CAPTION, 7, FORMAT, ">total:", ">avg:") do |x|
+  tf = x.report("for:")   { for i in 1..n; a = "1"; end }
+  tt = x.report("times:") { n.times do   ; a = "1"; end }
+  tu = x.report("upto:")  { 1.upto(n) do ; a = "1"; end }
+  [tf+tt+tu, (tf+tt+tu)/3]
+end
+```
+
+The result:
+
+```
+             user     system      total        real
+for:      0.950000   0.000000   0.950000 (  0.952039)
+times:    0.980000   0.000000   0.980000 (  0.984938)
+upto:     0.950000   0.000000   0.950000 (  0.946787)
+>total:   2.880000   0.000000   2.880000 (  2.883764)
+>avg:     0.960000   0.000000   0.960000 (  0.961255)
+```
 
 ## Development
 
@@ -32,4 +135,4 @@ To install this gem onto your local machine, run `bundle exec rake install`. To
 
 ## Contributing
 
-Bug reports and pull requests are welcome on GitHub at https://github.com/hsbt/benchmark.
+Bug reports and pull requests are welcome on GitHub at https://github.com/ruby/benchmark.
diff --git a/benchmark.gemspec b/benchmark.gemspec
index 99f0eeb..c2faac7 100644
--- a/benchmark.gemspec
+++ b/benchmark.gemspec
@@ -8,8 +8,8 @@ Gem::Specification.new do |spec|
   spec.authors       = ["Hiroshi SHIBATA"]
   spec.email         = ["hsbt@ruby-lang.org"]
 
-  spec.summary       = %q{Write a short summary, because RubyGems requires one.}
-  spec.description   = %q{Write a longer description or delete this line.}
+  spec.summary       = %q{a performance benchmarking library}
+  spec.description   = spec.summary
   spec.homepage      = "https://github.com/ruby/benchmark"
 
   spec.metadata["homepage_uri"] = spec.homepage