The acquisition of German participle inflection was investigated using spontaneous speech samples from six children between 1 ; 4 and 3 ; 8 and ten children between 1 ; 4 and 2 ; 10 recorded longitudinally at regular intervals. Child-directed speech was also analyzed. In adult and child speech weak participles were significantly more frequent than strong participles. Children's errors involved all elements of participle marking. All error types, including over-regularization, occurred from the beginning alongside correct forms. Errors decreased significantly over age. Over-regularization in the sense of -"t" affixation on strong verbs was significantly more frequent than erroneous -"en" suffixation on weak verbs but not than prefix and suffix omission. On participles with stem vowel change erroneous stem vowel was significantly more frequent than correct stem vowel with suffix error alone. Error patterns are explained in terms of frequencies, and participle inflection being learned as part of general verb inflection.