The literature on spelling and spelling development suggests there is a strong relationship between spelling and phonology (Bruck & Treiman, 1990; Caravolas, Hulme & Snowling, 2001; Craig, 2006; Gindri, Keske-Soares & Mota, 2007). Spelling, however, is considerably less researched than reading (Caravolas, Humle & Snowling, 2001). Spelling difficulties are known to be more persistent in people with reading and writing disabilities, even when their reading has become acceptable (Høien & Lundberg, 1999) but more research is needed in this area. Assessment and detailed knowledge of the difficulties is of great importance in order to provide the appropriate help for children with reading and writing disabilities (Frisk, 2010; Magnusson, Nauclér, & Reuterskiöld, 2008). The purpose of the present study was to develop and try out a phonologically based spelling test for children, with focus on medial phonemes. The study contained 150 pupils in grade 1 and 2 as well as pupils in remedial teaching due to reading and spelling difficulties in the same grades. In addition to spelling, all pupils were tested for reading ability, phonological awareness, nonverbal intelligence and auditory discrimination. Misspellings were analysed with three quantitative and one qualitative classification methods. Results showed that the spelling test based on analyse of medial phonemes captured misspellings to the same extent as the other quantitative classification method.  Pupils in grade 2 received significant higher results in the spelling test than pupils in grade 1. The group of typically developed pupils had significantly better results than the pupils with reading and writing disabilities. Results also showed that real words were significantly easier to spell than non-words. Moreover, significant correlations between spelling and reading ability, and spelling and phonological awareness, were found. The strong correlation between spelling ability and phonological awareness, and the fact that children with reading and writing disabilities performed poorly on spelling of non-words, lead to the conclusion that spelling and phonology are closely related, which is supported by the literature (Bruck & Treiman, 1990; Caravolas, Hulme & Snowling, 2001; Craig, 2006; Gindri, Keske-Soares & Mota, 2007).