diff --git a/bilby/gw/prior.py b/bilby/gw/prior.py
index cd2fcd92e7e5f710e8e2e5f8e5f16c8b79baa2ca..2ff4128eebd60cae69c742352ba6a27627aad065 100644
--- a/bilby/gw/prior.py
+++ b/bilby/gw/prior.py
@@ -193,7 +193,7 @@ class AlignedSpin(Interped):
 
 
 class BBHPriorDict(PriorDict):
-    def __init__(self, dictionary=None, filename=None):
+    def __init__(self, dictionary=None, filename=None, aligned_spin=False):
         """ Initialises a Prior set for Binary Black holes
 
         Parameters
@@ -203,8 +203,13 @@ class BBHPriorDict(PriorDict):
         filename: str, optional
             See superclass
         """
+        basedir = os.path.join(os.path.dirname(__file__), 'prior_files')
         if dictionary is None and filename is None:
-            filename = os.path.join(os.path.dirname(__file__), 'prior_files', 'binary_black_holes.prior')
+            fname = 'binary_black_holes.prior'
+            if aligned_spin:
+                fname = 'aligned_spin_' + fname
+                logger.info('Using aligned spin prior')
+            filename = os.path.join(basedir, fname)
             logger.info('No prior given, using default BBH priors in {}.'.format(filename))
         elif filename is not None:
             if not os.path.isfile(filename):
@@ -257,7 +262,7 @@ class BBHPriorDict(PriorDict):
 
 class BNSPriorDict(PriorDict):
 
-    def __init__(self, dictionary=None, filename=None):
+    def __init__(self, dictionary=None, filename=None, aligned_spin=True):
         """ Initialises a Prior set for Binary Neutron Stars
 
         Parameters
@@ -267,6 +272,8 @@ class BNSPriorDict(PriorDict):
         filename: str, optional
             See superclass
         """
+        if not aligned_spin:
+            logger.warning('Non-aligned spins not yet supported for BNS.')
         if dictionary is None and filename is None:
             filename = os.path.join(os.path.dirname(__file__), 'prior_files', 'binary_neutron_stars.prior')
             logger.info('No prior given, using default BNS priors in {}.'.format(filename))
diff --git a/bilby/gw/prior_files/aligned_spin_binary_black_holes.prior b/bilby/gw/prior_files/aligned_spin_binary_black_holes.prior
new file mode 100644
index 0000000000000000000000000000000000000000..52649990cf3ba75125caa21572efa01fcf9ddf84
--- /dev/null
+++ b/bilby/gw/prior_files/aligned_spin_binary_black_holes.prior
@@ -0,0 +1,19 @@
+# These are the default priors we use for BBH systems.
+# Note that you may wish to use more specific mass and distance parameters.
+# These commands are all known to bilby.gw.prior.
+# Lines beginning "#" are ignored.
+mass_1 = Uniform(name='mass_1', minimum=5, maximum=100, unit='$M_{\\odot}$')
+mass_2 = Uniform(name='mass_2', minimum=5, maximum=100, unit='$M_{\\odot}$')
+# chirp_mass = Uniform(name='chirp_mass', minimum=25, maximum=100, unit='$M_{\\odot}$')
+# total_mass =  Uniform(name='total_mass', minimum=10, maximum=200, unit='$M_{\\odot}$')
+# mass_ratio =  Uniform(name='mass_ratio', minimum=0.125, maximum=1)
+# symmetric_mass_ratio =  Uniform(name='symmetric_mass_ratio', minimum=8 / 81, maximum=0.25)
+chi_1 =  bilby.gw.prior.AlignedSpin(name='chi_1', a_prior=Uniform(minimum=0, maximum=0.8))
+chi_2 =  bilby.gw.prior.AlignedSpin(name='chi_2', a_prior=Uniform(minimum=0, maximum=0.8))
+luminosity_distance =  bilby.gw.prior.UniformComovingVolume(name='luminosity_distance', minimum=1e2, maximum=5e3, unit='Mpc')
+dec =  Cosine(name='dec')
+ra =  Uniform(name='ra', minimum=0, maximum=2 * np.pi)
+theta_jn =  Sine(name='theta_jn')
+# cos_theta_jn =  Uniform(name='cos_theta_jn', minimum=-1, maximum=1)
+psi =  Uniform(name='psi', minimum=0, maximum=np.pi)
+phase =  Uniform(name='phase', minimum=0, maximum=2 * np.pi)