diff --git a/tests/test_bcftools_validation.py b/tests/test_bcftools_validation.py
index e62a089..e84158c 100644
--- a/tests/test_bcftools_validation.py
+++ b/tests/test_bcftools_validation.py
@@ -117,7 +117,8 @@ def run_vcztools(args: str, expect_error=False) -> tuple[str, str]:
             "view --no-version -i 'FILTER~\"VQSRTrancheINDEL99.00to100.00\"'",
             "1kg_2020_chrM.vcf.gz"
         ),
-        ("view --no-version -i 'INFO/AC>2'", "chr22.vcf.gz")
+        ("view --no-version -i 'INFO/AC>2'", "chr22.vcf.gz"),
+        ("view --no-version -i 'INFO/AC[0]>2'", "chr22.vcf.gz")
     ],
     # This is necessary when trying to run individual tests, as the arguments above
     # make for unworkable command lines
diff --git a/tests/test_filter.py b/tests/test_filter.py
index 83be0b6..f90fce8 100644
--- a/tests/test_filter.py
+++ b/tests/test_filter.py
@@ -38,20 +38,13 @@ def test_invalid_expressions(self, parser, expression):
             ('DP="."', filter_mod.UnsupportedMissingDataError),
             ("ID!=@~/file", filter_mod.UnsupportedFileReferenceError),
             ("INFO/TAG=@file", filter_mod.UnsupportedFileReferenceError),
-            ("INFO/X[0] == 1", filter_mod.UnsupportedArraySubscriptError),
-            ("INFO/AF[0] > 0.3", filter_mod.UnsupportedArraySubscriptError),
             ("FORMAT/AD[0:0] > 30", filter_mod.UnsupportedArraySubscriptError),
-            ("DP4[*] == 0", filter_mod.UnsupportedArraySubscriptError),
             ("FORMAT/DP[1-3] > 10", filter_mod.UnsupportedArraySubscriptError),
             ("FORMAT/DP[1-] < 7", filter_mod.UnsupportedArraySubscriptError),
             ("FORMAT/DP[0,2-4] > 20", filter_mod.UnsupportedArraySubscriptError),
             ("FORMAT/AD[0:*]", filter_mod.UnsupportedArraySubscriptError),
             ("FORMAT/AD[0:]", filter_mod.UnsupportedArraySubscriptError),
             ("FORMAT/AD[*:1]", filter_mod.UnsupportedArraySubscriptError),
-            (
-                "(DP4[0]+DP4[1])/(DP4[2]+DP4[3]) > 0.3",
-                filter_mod.UnsupportedArraySubscriptError,
-            ),
             ("binom(FMT/AD)", filter_mod.UnsupportedFunctionsError),
             ("fisher(INFO/DP4)", filter_mod.UnsupportedFunctionsError),
             ("fisher(FMT/ADF,FMT/ADR)", filter_mod.UnsupportedFunctionsError),
@@ -261,6 +254,25 @@ def test_evaluate_type_operation(self, expression, expected):
         result = fee.evaluate(numpify_values(data))
         nt.assert_array_equal(result, expected)
 
+    @pytest.mark.parametrize(
+        ("expression", "expected"),
+        [
+            ("INFO/AC>=2", [[0, 0], [1, 1], [0, 1], [1, 0]]),
+            ("INFO/AC[*]>=2", [[0, 0], [1, 1], [0, 1], [1, 0]]),
+            ("INFO/AC[0]>=2", [0, 1, 0, 1]),
+            ("INFO/AC[1]>=2", [0, 1, 1, 0]),
+        ],
+    )
+    def test_evaluate_array_subscripts(self, expression, expected):
+        data = {
+            "variant_AC": [[1, -1], [5, 4], [1, 4], [2, -1]],
+        }
+        fee = filter_mod.FilterExpression(
+            field_names={"variant_AC"}, include=expression
+        )
+        result = fee.evaluate(numpify_values(data))
+        nt.assert_array_equal(result, expected)
+
     @pytest.mark.parametrize(
         ("expr", "expected"),
         [
diff --git a/vcztools/filter.py b/vcztools/filter.py
index b5f0baa..b519a5e 100644
--- a/vcztools/filter.py
+++ b/vcztools/filter.py
@@ -99,6 +99,11 @@ class Number(Constant):
     pass
 
 
+class Integer(Constant):
+    def eval(self, data):
+        return int(self.tokens)
+
+
 class String(Constant):
     def __init__(self, tokens):
         super().__init__(tokens)
@@ -146,11 +151,29 @@ def referenced_fields(self):
         return frozenset([self.field_name])
 
 
+class IndexAny(Constant):
+    def eval(self, data):
+        return Ellipsis
+
+
 class IndexedIdentifier(EvaluationNode):
     def __init__(self, tokens):
-        # The tokens here are the already resolved idenfitier
-        # and the index
-        raise UnsupportedArraySubscriptError()
+        token = tokens[0]
+        # The tokens here are the already resolved identifier
+        # and the index - but only in the case of a single element
+        # index (an int), or any (*)
+        if len(token) > 2:
+            raise UnsupportedArraySubscriptError()
+        self.identifier = token[0]
+        self.index = token[1]
+
+    def eval(self, data):
+        val = self.identifier.eval(data)
+        ind = self.index.eval(data)
+        return val[:, ind]  # index samples dim
+
+    def referenced_fields(self):
+        return self.identifier.referenced_fields()
 
 
 class RegexOperator(EvaluationNode):
@@ -523,9 +546,11 @@ def make_bcftools_filter_parser(all_fields=None, map_vcf_identifiers=True):
     # TODO we need to define the indexing grammar more carefully, but
     # this at least let's us match correct strings and raise an informative
     # error
+    index_single_element_expr = pp.Word(pp.nums).set_parse_action(Integer)
+    index_any_element_expr = pp.Literal("*").set_parse_action(IndexAny)
     index_expr = pp.OneOrMore(
-        pp.common.number
-        | pp.Literal("*")
+        index_single_element_expr
+        | index_any_element_expr
         | pp.Literal(":")
         | pp.Literal("-")
         | pp.Literal(",")